Cisterns were the most important buildings of a Byzantine city because they were built in order to keep the water. They were constructed in huge scales. Underground cistern is one of them but except the big ones, there were other cisterns under the other buildings. They were built in small scale. They were vital for a city surrounded by walls.

In the same time they can be considered as the wonders of Roman engineering. It is told that tunnels were constructed between the imperial buildings. Underground cistern is a place that was built between 527 and 565. It is like a time capsule for the city. It hides some features from various ages. The pillars and sculptures are architectural items especially Medusa head.