The old line about being seen from space may sound tired, and it’s actually debatable, but it is an incredible feat that many of the series of long fortresses that were built from 6BC – construction continued well into the 16th century – are still standing. The 6,700km (4,163 mile) wall was built and maintained to protect the North of China from attack.
In pictures: 50 of the world's most beautiful things
In pictures: 50 things to eat before you die
In pictures: World's sexiest cities
You decide: The most boring places on the planet
Flying cruise ships, floating cities... travel of the future
