Deep beneath Sultanhamet, there is a curious site. Well below ground, the byzintine cisterns built by Emperor Justinia still exist. They had actually been forgotten about for ages and re-discovered. Locals who had houses would talk of using buckets on ropes to pull up fresh water from a hole in their basement, and sometimes even fish! They were re-discovered and opened as a tourist attraction, fish and all.
It was lovely, damp and dark down there. A good escape from the heat of midday.
There are two pillars with huge carved medusa visages.
They are mysterious in origin, which basically makes it an ideal tourist trap when you claim things like that. "We have no idea how these got here" and "it's a mystery who put these here and why". Sold!