Zhang Bi in Shanxi province is a small ancient fort where the village was built within the walls. The fortress was built on the top of a 1000m high cliff. Underground the village runs a winding set of tunnels at different levels, which were used as a defensive system during wars. The tunnels emerge on the edge of the cliff face, over looking the steep sides of a gorge with amazing views. The tunnel is 5km long with three levels, the first only 1-2m below ground, and the third 20m below ground. As we walked through the tunnels, we saw trap doors, water wells, communication holes, ambush areas, store rooms, stables for their horses and sleeping quarters (which were basically just a flattened pile of mud, can't imagine they'd have been very comfy). I found learning about the history of the fort really interesting, and with the village area still being lived in, the place had a very cultural feeling. Little muddy back alleys, high walls and old wooden gates and doors all added to the village's charms.