These cliff wall houses in Beijing's outskirts, have complex structure and ingenious design. It’s said to be excavated by a tribe during 581
AD to 907 AD, in a quiet valley less than 10
meters wide, nearly 100 thousand square meters of steep cliff wall are covered with various sizes of 117 cave rooms. As a result, tourists keep coming.
These cliff wall houses or cave houses are connected with each other through stone steps and stone ladders, very orderly. Each cave house is about 1.8 meters high, most has three
bedrooms, but only 1 bedroom has windows. The biggest cave room is about 20 square meters, whereas the smallest about 4 square meters, equipped with stone beds, stoves and closets and so on. Different cave rooms
have different functions, with a stone bed are for people, with a manger are for
horse...
Besides one cliff wall house similar to ancient palace, has 4 stone pillars
supporting the roof, and 2 small bedrooms on both sides, not only very tall and
spacious, but owns excellent indoor lighting and fine carving... why did ancient Chinese live in a steep cliff wall? because no definite historical records, it's still a mystery! 
The pictures are from here.
The pictures are from here.
