This is a massive ruin where you can to spend anywhere from an hour to a day. See stonework comparable to Machu Picchu, in a beautiful setting, with a fraction of the crowd.
Malaysia - Batu Caves - Exploring the cave temple, a free attraction
Free and easy to get to temple in a mountainside cave, just outside Kuala Lumpur
Thailand - Tiger Cave Temple, Krabi - Dodging monkeys on the climb to the giant Buddha
Mix a little culture, lots of stairs, stunning views, and a whole barrel of monkeys together and you get Tiger Temple.