Yerebatan Cernici cistern
UNDERGROUND WATER CISTERN, BASILICA CISTERN
Yerebatan Cernici (literally "Sinken Palace" in Turkish) is the largest underground water cistern in Istanbul. It is a very exciting and popular tourist destination, right below the ground near Sultanahmet Square and Hagya Sophia. You can walking around among the water underground and look at the beautifully illumated columns and pillars, creating a very special red and yellow light. It covers an area of 9 800 m and the roof rests on 336 columns. The Medusa heads, one upside down are captured from Greek buildings. Many concerts and movies have taken place in the cisterns.
It was built by the Romans, initially by Constantine, and extended by Justinian in the year 537. During the Byzantine times it was located right below the Stoa Basilica, thus it is sometimes called the Basilica Cistern.