Church at Beyazıt State Library
The remains of a three-aisled basilica were discovered at Beyazıt State Library in 2013. It was located east of the Forum of Theodosius, just north of the Mese. The church perhaps dates to the late 5th century. The apse of the southern aisle was probably used as a burial chapel at a later date, perhaps when opus sectile was added here. There are fragments of frescoes in the synthronon of the apse. Only its three apses survived, while the rest of the structure was probably destroyed during the construction the imaret of Beyazıt Mosque (now functioning as Beyazıt State Library).
Plan from Özgümüş et al.
“Report of the New Findings from Byzantine Istanbul” by Özgümüş, Ermiş & Yılmaz