After staying on the beach until 10 o'clock, you should stay in the shade, you can go to the St. Peter & Paul Orthodox Cathedral to admire the Greco-Roman architecture. The church got damaged in The World War II and was restored after a while. It should take around 20 minutes to visit.
After you saw the Orthodox chapel, you are ready to see The Great Mahmudiye Mosque with the same Byzantine and Romanian architectural elements, making it the most distinctive mosques in the area.