Turkish Hurriyet Daily News reports that a semicircular structure dated to the third century B.C. has been uncovered at the site of the Haydarpașa train station in Istanbul, which is located on the Asian side of the Bosporus. Archaeologist Mehmet Ali Polat said the region was once the northwestern port for the ancient city of Chalcedon.

This apsidal structure is thought to have been used as a sacred space, but the investigation has also uncovered traces of a large building that may have served as a warehouse, and a group of buildings that may have been a small summer palace, he explained.

source archaeology.org