It’s hard today to pinpoint the exact center of Istanbul. Like any other megacity, Istanbul has many centers that constellate outwards. But once upon a time, when Istanbul but still Constantinople, it was a city contained within city walls and its center was marked by a green serpentine porphyry column.
The only documented text about the serpentine column comes from the 17th-century travelogue Seyâhatnâme written by the Ottoman explorer Evliya Çelebi.
In the travelogue, it’s mentioned that architect Minar Sinan wanted to build Şehzade Mosque in the center of the city. After taking measurements, Sinan determined this point as the center and placed the serpentine column above it. Inspired by the tradition of the Byzantine Million, the column represented the center from which all distances were then measured.
The serpentine column has a diameter of 38 cm and a height of 128cm and is located at the southern corner of the exterior walls of Şehzade Mosque. It is easy to miss so you need to look for it. It’s on the edge of the sidewalk that leads onto a crosswalk. There is no special designation to mark its presence. Only a small placard with an outline of its history.