El Caminito del Rey (English:The King's pathway) is a walkway or via ferrata, now fallen into disrepair, pinned along the steep walls of a narrow gorge in El Chorro, near Álora in Málaga, Spain. The name is often shortened to El Camino del Rey.
The walkway has now gone many years without maintenance, and is in a highly deteriorated and dangerous state. It is one meter (3 ft) in width, and is over 700 feet (200 m) above the river. Nearly all of the path has no handrail. Some parts of the walkway have completely collapsed and have been replaced by a beam and a metallic wire on the wall. Many people have lost their lives on the walkway in recent years. After four people died in two accidents in 1999 and 2000, the local government closed the entrances. However, adventurous tourists still find their way into the walkway.
Here's a video of part of the path. I sent this to a friend of mine and he said "I was white-knuckling my couch as I sat here."
What may surprise you is that the video above looks pretty safe compared to the Huashan Hiking Trail in China.
EDIT - further reading shows that the trails aren't THAT dangerous, but they aren't necessarily easy either.
I'd still love to go there though: