The Library of Hadrian was built in A.D. 132 by Emperor Hadrian, was destroyed by the Herulae in A.D. 267, and was subsequently incorporated into the Late Roman fortification wall. It was repaired by the Roman eparch Herculius in A.D. 412, and in the 5th century the quatrefoil building of the Early Christian church was constructed in the centre of the peristyle court. Marble revetments and rich decoration characterize the building, which was associated with the Athenian empress of Byzantium, Eudocia. After its destruction, a three-aisled basilica was erected on its ruins in the 7th century, which was in turn superseded by the single-aisled church of Megali Panagia, in the 11th century. During the Turkish occupation it became the seat of the Voevode (Governor) and in 1835, the barracks of king Otho were erected in the place of the Voevodalik.
There was another church built into one of the outer walls of the Library of Hadrian. It is now only preserved a part of a wall and the post Byzantine wall painting on the façade of the Library, where are depicted Judas’ Betrayal, the Prayer in Gesthimani as well as saints on medals on the lower zone.It was a small, not fully developed cross-in-square church built next to the wall of the façade and the propylon of the library. Built by members of the Chalkokondyli family in the 12th century it was dedicated to Archangel Michael (Hagios Asomatos) by the founder, Michael Chalkokondylis. It is called “on the steps” (sta Skalia) after its position in the propylon of the Library. It was renovated during the post Byzantine years (1576) and demolished after 1843. In the floor of the main church and the narthex have been excavated eleven barrel-vaulted tombs, where members of the Chalkokondyli family used to be buried.

​Near the northern corner of the ruins of the Library of Hadrian is the Tzistarakis Mosque dating to the 18th century.