Near the Basilica Cistern, is a fragment of the original monument, the Milion Stone.
In the early 4th century, Emperor Constantine I the Great built the zero-mile marker on the road which led from Istanbul (Constantinople) to Rome. This became the starting-place for measuring the distances of all roads leading to important foreign cities.
The Milion Monument was the starting point of the great Roman road Via Egnetia that lead to European cities and the reference point for measuring all distances on it.
The Milion Stone is located across the street from Hagia Sophia.