The Basilica Cistern is the largest of several hundred ancient cisterns that lie beneath the city of Istanbul, Turkey.

Istanbul’s Basilica Cistern Museum reopened to visitors this summer after five years of meticulous restorations and a number of improvements.

People are reflected in the waters of the Basilica Cistern while visiting the historic site in Istanbul, Türkiye.

Known as “Yerebatan Sarnıcı” or “Sunken Cistern” in Turkish, the Basilica Cistern is one of the most popular historical destinations in Istanbul.

The head of Medusa is seen in the Basilica Cistern in Istanbul, Türkiye.

Located within walking distance of other world-renowned landmarks like the Hagia Sophia Grand Mosque and Blue Mosque, the basilica is the largest of several hundred ancient cisterns that lie beneath the city.

A view of the Basilica Cistern following its restoration in Istanbul, Türkiye.

Constructed in the sixth century during the reign of Byzantine Emperor Justinian I, the basilica was once part of a network started by the Romans and completed by the Byzantines and Ottomans to supply the city and its palaces with running water.

A statue is seen between columns in the Basilica Cistern after its restoration in Istanbul, Türkiye.

The cathedral-sized cistern rests on a total of 336 marble columns, each 9 meters (30 feet) tall, and its chamber is capable of holding 80 million liters of water.

Visitors walk along the Byzantine-era Basilica Cistern in Istanbul, Türkiye.

While the origin of the heads remains unknown, it is believed they were taken from a structure from the late Roman period and reused in the cistern.

A visitor takes a photograph of a statue in the Basilica Cistern after its restoration in Istanbul, Türkiye.