There used to be a large forum where Istanbul's Beyazit Square is today, which was called the Forum Tauri (Forum of the Bull) because of a huge bronze bull statue in its center. The forum was later enlarged by Theodosius the Great, and the forum took his name from then on. There is little left of the forum, save a few columns scattered along Ordu Caddesi. The columns, which feature a "peacock feather" motif, were later used in other buildings, such as the Basilica cistern and the Beyazit Hamam, which is now a bazaar. Keep an eye out when visiting these sites and you'll see them.