Basilica Cistern (Yerebatan) which opened its doors to the world again in 2022 with the most comprehensive and costly restoration work ever done by the Istanbul Metropolitan Municipality, is also biggest cistern in the world. Built by the Byzantine Emperor Justinian I (527-565), the cistern was endangered many times in its 1500-year history due to natural disasters such as earthquakes and was kept alive from time to time by strengthening works.