Kathmandu valley is described as "an enormous treasure house of art and sculptures", which are made of wood, stone, metal, and terracotta, and found in profusion in temples, shrines, stupas, gompas, chaityasm and palaces. The art objects are also seen in street corners, lanes, private courtyards and in open ground. Most art is in the form of icons of gods and goddesses. Kathmandu valley has had this art treasure for a very long time, but received worldwide recognition only after the country opened to the outside world in 1950.

Kathmandu valley contains art made of metal, terracotta, wood and what other substance?