The Milion is starting point of all ancient roman roads reaching the city of Constantinopolis in the Byzantine Empire and the zero-mile marker for figuring out the distances of all cities on earth. It thus served the same function as the Golden Milestone (Milliarium Aureum) in Rome/Italy.

The ruin of the Milion is in Cağaloğlu neighbourhood near the entrance of Basilica Cistern on the north corner of the Sultanahmet Square close to the tramline.