Southeast Asia is a gold mine when it comes to ancient temples. Whether it's the Khmer Empire temples of Cambodia, the pagodas and stupas of Bagan in Burma, or one of the many wonderful sites in Thailand, you'd be hard pressed not to bump into some beautiful temples. Bagan is probably my favorite in terms of the sheer number of temples and how they mix with the environment around them, but in terms of diversity of archaeological finds, I've not come across anything quite like Angkor Wat.
The vast displays of bas-reliefs depicting the different gods, goddesses and mythological beings are an impressive display of what man has accomplished. How it was accomplished, is a different matter entirely of which books and tv programs have delved into.
It makes me wonder, will we ever see this level of effort put into building huge religious structures ever again? We no longer live in a time where a King can order thousands of subjects to erect these massive monuments and tributes to the gods. Perhaps that's for the best overall, but it seems all we get nowadays are ever taller skyscrapers, which, while nice to marvel at, don't come anywhere near the awe of an Angkor Wat or the pyramids of Giza.