The Great Wall of China, in Chinese Simplified is 长城, which literally "long[长] wall[~城]".

The full name in Simplified is 万里长城, or "Ten Thousand[万] Li (unit of measurement ~1/2 km)[里] long wall[长城]".

The idea was that the wall would cover ten thousand li, a metaphorically endless border to defend China (in reality being longer than that). It was officially called 长城 in historical records, with the name "Ten Thousand Li Wall" (no 'city' in the name) reflecting more of the idea that the wall was really long. In English, however, it's most commonly referred to as the Great Wall of China.

[1] - 史记公书 (literally, Public Book of Historic Records) authored by Sima Qian (司马迁), Historian of the Han Dynasty

Sources:

The Great Wall: A Cultural History - Rojas, C.