1. El Caminito Del Rey, Spain

Known as the "Little Pathway of the King", this was built in 1905 and has had little to no repairs done until recently. Therefore, bold climbers enjoy braving the sections that are dangerous and completely disintegrated.
2. Siju Caves, Meghalaya
The Siju Cave in Meghalaya is the first limestone natural cave in India. It is also home to a flimsy rope bridge that connects the summits of two hills. Its wobbliness will make you freak out. Extra pants are always a good idea!

132 kms from Tura, Siju is famous for Dobakkol or the bat cave with impressive stalagmites and stalagtites.

It is one of the longest cave in the Indian Sub-continent and contains some of the finest river passages to be found any where in the world. There are magnificent limestone rock formations inside, especially named princes, Di's chamber by the excavators will fill any visitor with awe.