How many miles is the Great Wall of china

It is around 5,500 miles.

There isn't ONE single 'Great Wall of China'. The Chinese began building walls on their frontier FAR back in time. The first imperial dynasty, the Qin, in the late 3rd Century BC spent a lot of effort on consolidating and extending the walls of that period, and every dynasty since then has built a rebuilt different walls, often in varying locations depending on exactly where the frontiers were at any given time and changing strategic needs. At NO time in history was there really one single contiguous wall. The sections near Beijing which are usually seen by tourists are I believe 16th or 17th Century structures, part of walls built by the Ming and Qing dynasties.