If you're ever in Bhutan (and I do recommend it) one of the must-see/must-do items on your list should be a hike up to the Tiger's Nest. Without boring anyone with details, the Tiger's Nest is a monastery high in the Himlayas, where guru Rinpoche is said to have flown on the back of a tigress and meditated. Imagine that JRR Tolkien wrote "Lord of the Rings" as a Buddhist and you start to get the idea. Here's a little more detail and some pictures: http://en.wikipedia.org/wiki/Taktshang.

It's about a 3 hour hike, give or take, and the monastery is, I would guess, about 12,000 feet above sea level. If walking isn't your cup of tea, you can rent a donkey or horse at the bottom of the trail. The trail is good, and there's a cafeteria about 2/3 of the way up where you can order a meal that will be ready after you've gone up to the monastery and back. The view down the valley is spectacular.

It's highly worth it; only about 17,000 people visit Bhutan each year.