The majestic ancient temples of Cambodia’s Angkor Wat are of course a must see, and need at least a couple of days to look around. Despite, or perhaps because of, its rapid growth, Siem Reap town (where the accommodation options are situated) retains much of its character; and one doesn't have to wander far to experience its uniquely Cambodian charms.
There are many other parts of Cambodia worth visiting besides Angkor Wat: the capital Phnom Penh is a budding, quickly-evolving city and an intriguing destination, and unknown to many there are great beaches off the coast of Sihanoukville, jungles in the northeast and magnificent lakes and rivers with thriving communities living nearby. There are also the historic, Indochina-esque towns of Battambang in the west; and Kep and Kampot in the east, towards the Vietnam border.