History

The monastery began as a Temple of Helios and its monumental semicircular courtyard in front of the rotunda connected the temple to the Mese (main street). The 5th century Temple of Helios' rotunda was the second largest, after the Pantheon in Rome, in the Ancient World. As paganism declined the temple fell into disuse and the courtyard became known as the Amastrianum (property of a person from Amastris), becoming a marketplace and a place of executions.

However, in the 10th century the rotunda was converted into a cistern by Romanos Lakapenos and a palace was built on top to rival the Great Palace itself. He built the the Church of the Holy Anointing Oil on a substructure south of the palace to keep it level with the palace and act as a burial place for his family. Romanos later converted his palace into a nunnery when he became emperor and was later buried here.

In the centre of the Amastrianum lies the Modius, used to measure cereals and warn merchants of using false measures. The modius was placed here due to the forum's proximity to the Harbour of Theodosius and neighbouring wheat deposits.