We all know icebergs; we see a small part of an iceberg on the surface of water. We can realise that it is a giant when we see the bottom part of the iceberg. Istanbul is the same. Constantinapole is under the modern part of the city. The archeaologist still are discovering new tunnels and new cisterns under Istanbul.
According to the last news, some archeaologists discovered a cistern that has links to other underground cisterns. It means that there is an another Constantinapole under Istanbul. We have already legends of Constantinapole and it is so hard to imagine that you can think of the first undersea passage. Topkapı Palace was built on the great palace of Byzantines, you can see some secret ways to cisterns of this old palace today.
Istanbul is the center of history. It is accepted by all tourism authorities. You can visit Istanbul to travel in time till the capital of Byzantines.