Pambanan is the largest Hindu temple compound in Indonesia, just about one hour of car distance from the largest Buddhist monument in the world, Borobudur.
Built shortly after Borobudur, the Prambanan temple was abandoned and began to deteriorate. No one really knew why. It wasn't until some hundreds of years later that the Hindus moved out of Java and transfered to Bali. Famine perhaps?
The compound restoration started in 1918, and is still unfinished. After all, a temple will only be rebuilt if at least 75% of the original stones are available. Unfortunately, most have already been carted away illegaly.
Prambanan, Central Java, Indonesia
A UNESCO WorldHeritage Site