Constantinople's water supply was brought in via aqueduct, which meant it was vulnerable to enemy attack. So, Emperor Justinian built this massive Underground Cistern (and others like it) as a hedge against a long siege.
When the Ottomans took over, the cistern fell out of use and was forgotten. Centuries later, people started questioning why you could sink a well anywhere in this area and find an endless supply of fresh water. And even go fishing! After a bit of exploration, they re-discovered the Underground Cistern.
The entrance to the Underground Cistern is across the street from Aya Sofya.
When the Ottomans took over, the cistern fell out of use and was forgotten. Centuries later, people started questioning why you could sink a well anywhere in this area and find an endless supply of fresh water. And even go fishing! After a bit of exploration, they re-discovered the Underground Cistern.
The entrance to the Underground Cistern is across the street from Aya Sofya.