The Cistern of Philoxenos is the second largest subterranean water reservoir in Istanbul. The cistern with dimensions 64 by 56 m is located on the west of the Hippodrome. It was recently restored and connected to the nearby road with a gallery. The cistern was built by Philoxenos during the 4th century in the era of Constantine the Great. From 224 original columns there remain 212 today. The building is surrounded with thick walls and the brick vaults supported by columns which are a superposition of two columns joined by a marble ring and carrying caps without engravings are worth to see.

Small souvenir kiosks, café and the exhibition areas together with an excavated pond with four columns in the middle of the cistern for showing the original height of the cistern were added during the restoration.