In Tunnels! With 25 Science Projects for Kids, children ages 7 to 10 explore the fascinating world of passageways beneath the ground, dug deep within the earth through soil and rock. But why dig through rock to make a tunnel? Tunnels give people a way to travel and transport goods from one place to another. Readers learn about the engineering and construction that go into every tunnel made, whether it's being dug under roads, under oceans, or under cities.