It is across the Court House. It was made by one of the senators of the city, Philoxenos, to meet the water needs of the palace after moving capital of Roman Empire to Istanbul.
The Cistern of Philoxenos is in the size of 64 to 56 meters and consists of 244 columns. Pillars connected to each other by aqueduct carries the cross-vaulted ceiling. Many letters carved into the pillar belongs to the workers in the construction of cistern. The cistern is used as a touring venue and café