The Cistern was built between 428 and 443. Emperor Theodosius named the Cistern after himself. It was part of the main water system of the city. There was a lack of water sources in the town. This leads the Byzantines to build lots of cisterns to save as much rainwater as they can, in these cisterns. They used the water from these cisterns, only in an emergency, during droughts or sieges.The Cistern is made of brick, local limestones, and hydraulic mortar. It is around 24x40 meters. Thirty-two marble columns, with Corinthian-style capitals, are supporting the roof. It was restored very well recently and opened as a museum to the public.