This is also known as the Yerebatan Saray?, or Sunken Palace. It was originally constructed by that great builder, the Emperor Justinian in the sixth century, on a site to be near the old palace. It was also known as the Basilica Cistern. It is one of the biggest of the Byzantine cisterns, being 140 metres by 70 metres (154 by 77 yards). It has no less than 336 columns, each 8 metres (about 26,5 it) high.
As in the equally famous Thousand and One Columns, no part of the pillars have remained in the ground. It is the only one of the old Byzantine cisterns which still contains water, which is brought from the reservoirs in the Forest of Belgrad. Electric light has been installed and it is possible to go for a row in it in a boat. It is one of the most impressive of all Byzantine remains, a fitting offset to the wonderful building of Justanian nearby, Aya Sofya, that is, Hagia Sofia.
Continuing from the Underground Cistern in the direction of the trams, we come to Hagia Sofya Place with the Aya Sofya Museum. To the south of the Museum is the Mosque of Sultan Ahmet. Here too we see the Obelisk and the Hippodrome Place, the Atmeydani, to-day the Place of Sultan Ahmet. And then, on the north side, there is the old Church of St. Irene, the Palace of Topkapi, the Topkapi Museum, the Museum of the Ancient East, the Archaeological Museum and the Tile Kiosk.