Angkor Wat (Angkor Temple) is one huge, huge temple compound on a Unesco site that has many other temples. There are lots of temples in the Siem Reap area.
If you go to Angkor, stay at the Two Dragons Guesthouse (owner is acquaintance of mine) and also see the Landmine Musem and Orphanage on the road to Banteu Sreay temple. (Canadian director is also acquaintance, I'll send you his name)