Construction History, Kapellbrücke Luzern

Hochschule Luzern, FH Zentralschweiz Focus Lectures

CONSTRUCTION HISTORY KAPELLBRÃœCKE, LUZERN

AN ILLUSTRATED INTRODUCTION TO THE CHAPEL BRIDGE IN LUZERN, SCHWEIZ AKSEL STAVE ERVIK

Fokusvorlesung -FS16 Horw, 10.06.2016

Students: Aksel Stave Ervik Steinhofstrasse 15g 6005 Luzern, Schweiz

Professor: Dr. Mario Rinke

Lucerne University of Applied Sciences and Arts Hochschule Luzern Technik und Architektur

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Content Introduction History, purpose and function Architectural Concept Structural Concept Material composition Bearing wooden structure and load transfer Covering structure Entrances The Tower Paintings, fire and restoration Bibliography

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Introduction Front Page, Pic 1.

Own photo, taken in April 2016

The Chapel Bridge (Kapellbrücke) in Luzern is a construction that unites the two parts of the city Luzern in central Switzerland, crossing the river Reuss. With its 2021 meters, it is the second longest covered wooden bridge in Europe. Luzern is set 438 meters above the ocean, in a mild and moderate climatic barrier between the north and south of Switzerland, with ca. 138 days of rain per year.2 Almost 300 km from the Sea (Mediterranean), Reuss transports fresh water from Lake Luzern northwards until it flows into the river Aare at Brugg.

History, purpose, and function 13653 is believed to be the year the bridge was constructed, and it was originally 75 meters longer than it is today. In the Luzern old town book (Alter Luzerner Stadtbuch) it is referred to as the “new bridge” (Neubrücke) in 1637. A fill-in of the banks surrounding the river in 18354 led to the removal of 1/4th5 of the bridge. As the Musegg City Wall in the Northwest, the Chapel Bridge functioned as an important part of the city’s defence from they were both built in the 14th century. As the Musegg Wall and its nine towers functioned as a rampart system to protect the city from intrusions from the north, the role of the bridge was to serve a protection from intruders passing the lake of Luzern. For almost 300 years, the bridge mainly served as a practical fortress for the city, also controlling the traffic up the river.

Kapellbrücke was also connected to the important Hofbrücke. This bridge crossed the part of the inner lake that is today filled in to be Schwanenplatz and Schweizerhofquai. Together they formed the lakeside border and eastern defence of Luzern.

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1

https://de.wikipedia.org/wiki/Kapellbrücke

2

http://www.climatedata.eu/climate.php?loc=szxx0021&lang=en

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Die Kapellbrücke zu Luzern, page 8

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https://de.wikipedia.org/wiki/Kapellbrücke

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http://www.maison-du-chapeau.ch/luzern/kapellbruecke.php

Pic 2. Model view of the house

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Luzern seen from south. Illustration from the city plan of 1597. As seen on these pictures are both the Kapellbr端cke in the middle, and the Hofbr端cke to the right.

Pic 3.

This drawing from Petermann Etterlin was made in 1507, and is the oldest known portrait of Luzern. Here, we see as on the other picture the importat fortress function the Kapellbr端cke and Hofbr端cke served together with the towered ramparts on Musegg. The city were already set on both sides of the river, also giving the bridge a infrastructural importance.

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Pic 4.

Illustration drawing showing the bridge from northeast, uniting the two parts of the city separated by the river. In the lower right corner is the tower belonging to the city hall, or „Rathaus“.

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Architectural Concept Individual parts The Chapel Bridge consists mainly of two parts, the tower and the covered walkway. As the architectural language of the structure changes at the two entrances to the bridge, both of them are empazised as own individual parts in this text. In addition, the illustration below (Pic 7) will be used to explain which part of the bridge is being discussed. Set on a somewhat 100 pillars on the river floor, the bridge mender over the river with two powerful jacks in position.

Set on one of the jacks is the 43-meter stone tower, serving various functions for the city during its lifespan. Today, the bridge is a large tourist attraction, mainly because of its rareness and strong position in the history of the city. In addition, the bridge is home to a famous series of triangular paintings dating from the 16th century6, spread along the interior gables of the covered walkway.

Pic 5.

Map photo of the bridge with its jacked shape, with the tower close to the southern riverbank.

Pic 6.

Aerial photo of the bridge as it stands today, with the neighbouring Seebrucke (1870) to the left, and the Rathaussteg (1961) to the right in the direction of the river.

Pic 7.

Illustration drawing of the bridge as seen when approached from the western side. This illustration will be used when showing different parts during this document.

The left part of the picture shows the north entrance, while the left shows the southern one.

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Paintings mounted in 1610, Die KapellbrĂźcke zu Luzern, page 4

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Structural Concept Material composition Three materials are mostly used in the construction of the bridge.

Stone, wood and ceramic tiles. The tower is constructed of natural stone, while the roof structure and the rest of the bridge is woodwork. Wooden dowels join the wood, and the roof is covered by tiles on both the walkway and the tower.

Pic 8.

Photo showing the joints of the interior gables of the bents when it was reconstructed in 1994.

Pic 9.

As the roof was being renovated in 2015, some parts of the construction also had to be replaced.

Shown here is a brace that stabilizes the joint between one of the posts and the beam.

Bearing wooden structure and load transfer Although physically connected to the tower, the covered walkway is an individual part of the bridge carrying its own weight. It is connected to the riverbanks on two sides, but the weight of the construction is distributed through the more than 100 pillars that stand on the river floor. As shown on the illustration, the central part of the bridge has a slightly different way of going into the water. Here, the wooden pillars are changed in favour of concrete pillars. The covered walkway is assembled by series of bents7, which are timber frame brackets or trusses. I choose to use the expression ‘’bent’’ in this text.

A bent is a structural template that is repeating on parallel planes along the structure. It consists of two posts, a beam and two braces.

In addition, it has god two rafters set diagonally on top of the beam to form a triangle bearing the roof. Usually, the braces are attached to the posts and the beam using wooden dowels in a harder material. The wood type on the dowels at this bridge is uncertain. What is special with the structure in the Kapellbrücke, is that the braces are extended all to the top of the triangle, also functioning as rafters.

This results in a steep version of the scissor timber thrust that is very stabile in thoughts of horizontal forces. When constructing in a river, this is surely a good idea. The direction of the walkway changes at two points, resulting in a kink that needs an additional structure to the bents. The consistent sequences of bents, I will refer to as the northern, the southern and the central part of the bridge.

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https://en.wikipedia.org/wiki/Timber_framing

Pic 10.

Illustration drawing an assembled bent, consisting of one vertical pillar on each side, an overlaying beam as well as the inner and outer rafters. The inner ones are an extension of the braces, while the outer ones are rested on top of the longitudinal beams, creating an overhang for the roof. The top beam is rested on the scissored inner rafters, locked in place by the outer ones.

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Pic 11.

The southern part of the bridge.

Pic 12.

Base bent on the southern part.

Pic 13.

The central part of the bridge.

The southern part of the walkway is elevated from the pavement by 6 steps, a total height of 60 cm from street level. The first, irregular entrance bent is followed by 3 regular bents, each set with a 3,5 m distance. This part of the bridge is approximately 15 m long (including crossing the central part), and set on wooden pillars. The pillar base is illustrated in picture 12 and differs from the pillars supporting the northern part. As this part of the bridge is quite short and the river shallower, the base structure is lighter and a bit simpler. The wooden base bents are constructed as a 2x4m frame of thick pillars bound together by a central diagonal cross, with one of the sides resting on stones on the river floor. After the third bent, the central part of the walkway meets it in an angle of 50° east. Where the southern and the central parts meet, the central part exceeds the southern one with half a meter west in plan. This form a small balcony edge set between the regular and the irregular bent.

The central part of the walkway consists of 14 complete bents of the same dimension as in southern part of the bridge. In difference from the other parts of the bridge, this one stands on casted concrete pillars. This seems to have been the case also before the fire in 1993, although not specifically mentioned in any written document. On the northern side of the tower, the direction of the walkway slightly curve8 into the direction of the northern part, and unite as one. The curve is made by a slight difference in position of the bents, without needing a secondary source of support.

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Curves 8-10° over a distance of 11,5 meters. Measures taken by author.

The northern part of the walkway is made up by 32 bents. It is the longest part of the bridge, measuring 130 meters. The bents follow the same construction and layout as the rest of the bridge, but set on a different base structure. As shown on the illustration, the base on the northern part is set up by three pillars aside each other, the outer two ones slightly inclined to the central one. Each of the outer ones are again stabilised by a stiffener of a bit smaller dimension, set diagonal to the central one, together forming a V shape. The stiffeners meet the central pillar in the same height as the water, revealing them when the tide is lower than normal. The three foot-pillars forming a bent that holds the bridge are referred to as “Jochs� in German. It is 8 meters between each set of them, and they are up to 12 meters tall, going at most 8 meters down below the river surface through the floor of it9.

Pic 14.

The northern part of the bridge.

Pic 15.

Illustration drawing showing three of the base bents, with an 8 meter distance. The point where they are interconnected is also where the waterline usually run.

The floorboards rests on the longitudinal beams set on top of the base bents, as does the wooden parapets.

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Handwerk in der Denkmalpflege, Neue Luzerner Zeitung, 16. August 2013 (page 44)

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Pic 16.

Roofcovering of the bridge. The tiles are a mixture of sharp and half round Beavertail tiles, with the sharp edged ones highly overrepresented.

Pic 17.

In this photo, the tiles connection to the underroof is clear.

The small bumps locking them here rests on the underlying horizontal wooden ribs, also with thin wooden pieces in the joint between the tiles. The latter is to make the roof compeletely water tight, and to make sure that the stones don‘t rest directly on each other.

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Covering structure On the roof, the ceramic tiles are attached to the horizontal wooden rood ribs without any kind of nails. They are locked by small bumps in the surface, held down by pressure of the above tile. The distance between each horizontal wooden rib is about 30 cm, and on the area above the entrances they are laid three and three with a smaller gap. The type of ceramic tiles is typical for the region, and burned to a medium rust red colour. They are normally seen on older buildings from the south of Germany through Switzerland, and are mostly referred to as Beaver Tail Tiles, or “Biberschwanzziegel”10 in German language. The name derives from their half round shape at the exposed part, reminding of a beaver’s tail. The tiles we see on the bridge today, were donated by the city of Bern after the bridge’s last fire. Formerly laid on old Bern houses, these tiles were kept in storage and given as a contribution to the restoration works in 1994. In total, a number of 35 000 of these tiles were given from Bern City under the restoration11.

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http://www.swissbrick.ch/produkte/dachziegel/falzziegel-2

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Handwerk in der Denkmalpflege, Neue Luzerner Zeitung, 16. August 2013 (page 44)

On the Walls, the wooden parapets on each side are assembled by 14-30 cm wide and 120-150 cm high boards. They protrude down the side of the bridge with about 30 cm on each side, and are set with a minimal distance to each other. Particularly special about the parapets is that the eastern side of the bridge are up to 30 cm higher than the western one. This is a continuation of a former function, when the bridge functioned as a fortress to the east. In order to seek shelter and spy on the enemy, this differentiation was given.

In addition, protruding wooden cases cover the top beam of the wooden base. In the shape of a steep right triangle, they wrap the meeting point between the parapets and the horizontal top beams of the base bents. These shelter them from heavy water and thereafter also rot.

Another action taken to prevent the climatic affections are the downwards lengthening of the parapets in the area around the base bents.

None of the wooden works on the river are painted, but in their natural state and exposed.

The floors of the covered walkway is laid by 16 to 27 cm thick wooden boards, tightly goined together. They are made with a tongue and groove, insuring a tight joint. Small gaps are left between them and the longitudinal beams of the base bent, to let out any water that might get to the floor under heavy rainstorms.

Pic 18.

Photo of the western parapet, illustrating its lower position relating to the eastern one.

Pic 19.

Photo example of a protruding wooden case set to protect the end of the top beam of the base bents.

Pic 20.

Interior photo of how the floor meets the longitudinal beams.

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Pic 21.

Photo of the northern entrance to the bridge as it appears today.

Pic 22.

1890 painting of the former north entrance to the bridge.

The Entrances The bridge is connected to the river bank on two sides, the Altstadt in the north, and the Neustadt in the south. None of the entrances retain their original architectural design, and have both been changed several times. It was shortened by 28 meters in 1835, and by another 16 meters after a fire in 1863. The last shortening of the bridge happened on the north entrance in 1869 during the construction of the Rathausquai12. The illustration shows the state of the north entrance before it was last shortened and got its present expression. As we can see, the new alteration was done in a much richer style and more complex construction. Although not very decorated beside the braces, the jerkinhead gabled structure clearly emphasize references that is usually seen on grand chalets and outbuildings along the Swiss country side. With spires on both two gables of the northern entrance, it is clear that this was to be expressive. With an increasing tourism after the railways entry in 1859, as well as the river and lakeside promenads like Jesuitenquai and Schweizerhofquai, the Swiss attention towards their own city and heritage was going through a change.

The city saw large and lavish hotels and steamboats opening, and one can therefore see the architecture of this entrance as a part of the development at this time. Perhaps was this a sort of “Heimatschutz�13, a proud reference to their own building heritage and history.

Pic 23.

Photo of the southern entrance to the bridge as it appears today.

Pic 24.

1835 drawing of the bridge.

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http://www.maison-du-chapeau.ch/luzern/kapellbruecke.php

13

https://en.wikipedia.org/wiki/Heimatschutz

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Pic 25.

Illustration drawing of the way the northern entrance meets the pavement. On this side, one has to go up two series of 6 steps, while it on the southern side is only one series of 6 steps. This difference in height of almost half a meter is a result of a difference in heigh between the quays. Also Illustrated is the level of constructional decoration on this part of the bridge, remarkably higher than the one on the southern side.

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Pic 23. Cover of the book „The dynamics of architectural from“

by Rudolf Arnheim

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The Tower Close to the left bank on the south side of the bridge is the octagonal watertower. The title can be misleading, as it has never contained water. The name simply comes from its position in the water. It is 43 meters high, including the roof structure. Inside this is the spectacular 15 meter tall attic room, used for interrogations14. The tower is solely a stone structure, built up by variations of local natural stone.

Cut stones have been used to construct the eight strict corners of the tower, using the technique of a classical quoin structure. The quoin stones are cut in a way that allows them to rest tightly on each other, minimizing the joint between them. This strengthens the structure so it stands stronger and can be built taller. It was first mentioned taken in use in 139715, but is assumed to have been constructed before the bridge itself. The Book „Die Kapellbrücke zu Luzern“ refers to it as “Jahrhundert erbaute Wasserurm, im Jahre 1248 v.Chr entastanden” as it was mentioned in 139715. In the bottom is the prison cell ‘Verlies’16 where the walls are three meter thick. There are no windows and no doors here, and the space is entered through a staircase running the whole length of the structure. The first floor has a treasure chamber, while the second floor used to be a storage for the city archive- and treasures. Altogether, the tower has functioned both as watchtower, city archive, dungeons and torture chamber.17 From the outside, one easily see a small cast iron structure on top of the roof.

This is the formerly protection of the very famous stork nest18, that has not been in use for over 100 years now.

14

https://de.wikipedia.org/wiki/Kapellbrücke

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Die Kapellbrücke zu Luzern, page 8

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Fensterlose kerker, https://de.wikipedia.org/wiki/Kerker

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https://de.wikipedia.org/wiki/Kapellbrücke

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Historische Bauten, http://www.stadtluzern.ch/dl.php/de/0d68p-zjd2qf/histBauten.pdf

Opposite side, Pic 26.

The tower photograped from the pavement on therivers southern bank.

Pic 27.

The tower.

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Pic 28.

Illustration drawing highlighting the stone construction of the octagonal tower. As seen here, the quoin is created by shifting every other stone in the opposite ditection. The fill in stones are not carved, and have a larger amount of mortar between them. The wooden battlement structure on the top overhangs the stone structure, a method that is seen on other european fortresses from the 14th century.

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Pic 29.

On this illustration drawing the thick stone walls are readable. up to three meters thick, not only did they stabilize the tower, but also kept if safe from intrudors.

The cellar room undergoes the watersurface with one meter, all set with vaulted stone ceilings.

The staircase is constructed in stone as a part of the wall, and located at the western, less exposed facade facing the covered walkway.

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Paintings, fire and restoration

Pic 30.

A series of the restored paintings as they appear by night.

Pic 31.

The catastrophic fire of 1993 left most of the bridge in ashes, leaving only the tower, the entrances and a few bents with their paintings.

The Luzern Government were in the 16th century a number of prosperous and educated patriarchates. Hard efforts were put down by them to fight against the reformation, and as a religious propaganda, the series of paintings were ordered to decorate the wooden bridges of Luzern19. All of the paintings therefore resemble catholic motives. A series of exterior paintings like these are very rear, and found nowhere else in Europe. In Luzern, such paintings decorated both the Kapellbrücke, Mühlenbrücke and the former Hofbrücke20.

The Hofbrücke was the first to get such paintings21, and the Kapellbrucke received it’s a few years later. As the city of Luzern itself was not rich at this time, some of the richest families therefore financed the paintings. In return, they had their crests and monogrammes painted on them as an honour. This is considered to be the first sponsoring of public art in Luzern. The paintings themselves measures 150 to 181 cm wide and 95 cm tall. Most of them were painted on spruce boards, with some of them also on maple and linden boards22.

After the destructive fire of 18. August 199323, it was never a question not to rebuild the bridge. Already 14th of April the year after, the bridge was reopened. The same construction methods and layout for the bridge was used, but an earlier constructional shortcut in the base bents of the northern part were changed into a real functionally anchored knot. Although new tools were used in the construction, the joints and surfaces were to resemble the old ones. After the fire, only 47 out of the 158 famous paintings managed to be saved.

Of these, 30 has been restored and put back in their place.

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Der Bilderzyklus, http://www.maison-du-chapeau.ch/luzern/kapellbruecke.php (translated from German) 22

Die Bilder der Kapellbrücke in Luzern, page 10

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http://www.20min.ch/schweiz/zentralschweiz/story/Vor-20-Jahren-stand-in-Lu-

zern-die-Welt-still-20824685

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Pic 32.

One of the 150x95 cm gable paintings mounted at it‘s place. The pictures show catholic happenings from the country‘s past, decorated with the coat of arms of the family who donated it. All of them also have a text written on them.

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Pic 33.

Photo taken from the reconstruction of the bridge in 1994. The new structure contains fire alarms, sprinklers and video surveillance.

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Bibliography Litterary sources Die Kapellbrücke zu Luzern B. X. Weber, J. Bussmann Buchbinderei, Luzern 1918 B 103.XU.(1)GR4 Kapellbrücke und Wasserturm -Der Wiederaufbau eines Wahrzeichens im Spiegel der Restaurierung und Forschung.

Stadt Luzern, 1998.

Kleine Geschichte der Stadt Luzern Hier und Jetzt, Verlag für Kultur und Geschichte GmbH, Baden 2015 978-3-03919-369-1 Die Bilder der Kapellbrücke in Luzern Heinz Horat, 2015 Hier und Jetzt, Verlag für Kultur und Geschichte GmbH, ISBN 978-3-03919-368-4 Die Kapellbrücke. Das Wahrzeichen der Stadt Luzern Maihof Verlag, CH-6002 Luzern Maihof Druck, Luzern ISBN 3-9520027-7-1 Chapel Bridge Luzern Aura Fotobuchverlag, 2010 ISBN 978-3-9523375-2-3 Die Kunstdenkmäler des Kantons Luzern, Die Stadt Luzern I Adolf Reinle, 1953 ISBN 3-9061319-1-2 Handwerk in der Denkmalpflege Neue Luzerner Zeitung 16. August 2013 (page 44)

Webpages http://denkmalpflege-schweiz.ch https://de.wikipedia.org/wiki/Kapellbrücke https://en.wikipedia.org/wiki/Kapellbrücke http://www.maison-du-chapeau.ch/luzern/kapellbruecke.php http://www.lucerne4you.ch/home.html

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Figure references Pic. 1. Authors own photo, taken in April 2016 Pic. 2. Kapellbrucke zu Luzern, page 3 Pic. 3. https://de.wikipedia.org/wiki/Petermann_Etterlin Pic. 4. Authors own illustrations for the reader Pic. 5. Map photo, Google Earth. Taken May 2016 Pic. 6. Aerial photo, Bing Maps. Taken May 2016 Pic. 7. Authors own illustrations for the reader Pic. 8. Die Bilder der Kapellbr端cke in Luzern, page 104 Pic. 9. Chapel Bridge Luzern, page 80 Pic. 10. Authors own illustrations for the reader Pic. 11. Authors own illustrations for the reader Pic. 12. Authors own photo, taken in May 2016 Pic. 13. Authors own illustrations for the reader Pic. 14. Authors own illustrations for the reader Pic. 15. Authors own illustrations for the reader Pic. 16. Authors own photo, taken in May 2016 Pic. 17. Authors own photo, taken in April 2016 Pic. 18. Authors own photo, taken in May 2016 Pic. 19. Authors own photo, taken in May 2016 Pic. 20. Authors own photo, taken in May 2016 Pic. 21. Authors own photo, taken in April 2016 Pic. 22. Die Bilder der Kapellbr端cke in Luzern, page 106 Pic. 23. Authors own photo, taken in June 2016 Pic. 24. Die Bilder der Kapellbr端cke in Luzern, page 105 Pic. 25. Authors own illustrations for the reader Pic. 26. Authors own photo, taken in May 2016 Pic. 27. Authors own illustrations for the reader Pic. 28. Authors own illustrations for the reader Pic. 29. Authors own illustrations for the reader Pic. 30. Authors own photo, taken in June 2016 Pic. 31. http://www.20min.ch/schweiz/zentralschweiz/story/Vor-20-Jahren-stand-inLuzern-die-Welt-still-20824685 Pic. 32. Authors own photo, taken in May 2016 Pic. 33. http://www.zentralplus.ch/de/blogs/fundstuecke/25542/Die-Kapellbr端cke.htm

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