The Million Stone (Zero Stone) was the center of the Earth in antiquity and was regarded as the zero point of Rome.
Million Stone is considered to be the starting point of all ancient Roman roads to the city of Constantinople in the Byzantine Empire. Million Stone was also the zero point used to calculate the distance of other cities on earth to the city of Constantinople.
The Stone has the same function as “the Milliarium Aureum” in the Roma, city of Italy. It is thought that Byzantine was built in the 4th century by Emperor Constantine I, like many magnificent monuments built during reconstruction and capital city acquisition.
Million Stone in Istanbul (Sultanahmet Square)
To the right of the road from Hagia Sophia to Beyazıt, located on the exact corner and not nearly properly recognized today, is the source of “all roads come to Rome”. 
The distance to any point in the world was measured from the Million Stone. For example, the reason for the Romans to give the name of Hebdomon (Greek “seven”) to Bakırköy was 7 miles away from Million Stone.
The Stone was actually Tetrapylon when it was first made. So it’s a domed structure on 4 columns. Unfortunately, it was damaged over time.
In the Ottoman Empire period, this was also considered a trademark.
Million Stone Legend
The legend is not lacking when it comes to the Romans and Istanbul. One of the myths of the Million Stone is also shudder: not a single enemy soldier can pass beyond the Million Stone. Anyone who crosses that boundary will be killed instantly by an angel.
Actually, this myth is basically based on mythology. I have stated that the Million Monument was originally built as Tetrapylon. According to some historians, this building was actually a temple. It is a temple built for Tike in Greek mythology and fortune goddess in Fortism, which is called Fortuna in Roman mythology. This goddess, which means “luck” in ancient Greek language, also gave directions to the fate of the cities.
But neither the Catholic Latins invaded Istanbul in 1204 nor the Mayi of 1453, when the soldiers of Sultan Mehmed II of Fatih went beyond the Million Stone and did not find a legend, and Istanbul fell on both dates.
