How many miles would a roman citizen cover traveling in a straight line from byzantium to the coast of gaul?

Byzantium was the Ancient name of present-day Istanbul. It was also known with the name of Constantinople for a period in Ancient Antiquity. On the other hand, Gaul was the name given by the Romans to the territory where present day Gauls lived. It is roughly equivalent to areas of France, Belgium, Luxembourg, the Netherlands and Switzerland.

If a Roman citizen were to walk across that land in a straight line, he would cover about 1,500 miles.

The roman citizen would probably have traveled around 1,500 miles in a straight line from the city of Byzantium, now called Istanbul, to the coast of Gaul, The cost of France and Northern Italy nowadays.