Mogao Caves, China
The caves here are amongst the finest examples of Buddhist art in the world. There are 45,000 square feet of murals to savor, though the most rewarding visits take in around 7 or 8 of the best caves, where you will be guided by one of the site's qualified guides.
Photography is not allowed inside the caves, but some nice books can be bought from the museum on site. The best caves are probably those dating from the Tang period, when this region was at its zenith.
A couple of the caves house large statues of the Buddha - one, at over 34 m high it is one of the world's tallest.