The Milion Stone (Istanbul Metropolitan Municipality)

 byzantine, interesting place, zero kilometer sign, historic ruins

Center of Byzantine roading system. Distances were measured by their distance to this stone.
The Milion (Greek: Μίλιον or Μίλλιον, Míllion; Turkish: Milyon taşı) was a monument erected in the early 4th century AD in Constantinople (modern-day Istanbul, Turkey). It was the Byzantine zero-mile marker, the starting-place for the measurement of distances for all the roads leading to the cities of the Byzantine Empire. It thus served the same function as the Golden Milestone (Milliarium Aureum) in Rome's forum. The domed building of the Milion rested on four large arches, and it was expanded and decorated with several statues and paintings. It survived the Ottoman conquest of Constantinople in 1453 but had disappeared by the start of the 16th century. During excavations in the 1960s, some partial fragments of it were discovered under houses in the area.
en.wikipedia.org/wiki/Milliarium_Aureum

3D reconstruction:
byzantium1200.arkeo3d.com/milion.htm