Angkor, Cambodia. Photo by Samgarza.
This Khmer temple/urban complex was one of the most capital capitals in Asia in the 9th-14th centuries, 400 sq kms of stunningly carved, world beating wonders, including Angkor Wat.
Exploring this requires several days; see Angkor Wat and pinky Banteay Srei (25km away) for awesome carvings, Angkor Thom for huge style and imposing faces, Ta Prohm for jungle tangled temples; another 40 great ruins await your time but don’t stray off regular tracks, there are still land mines around.
The local town of Siem Reap is a pretty cool place, quite relaxed, not too much traffic and colourful streets in the evening when tourists are back from Angkor. ‘Pub Street’ and surrounds near the Old Market are lively and buzzing with an interesting variety of bars and restaurants.
Phnom Penh is just about worth a couple of days, while some beaches accessible via Sihanoukville (which is overbuilt, overcrowded and understyled) are beautiful and/or dippy hippy retreats such as Otres 1. Otres 2 is the place for grown ups while Ko Rong and Ko Rong Sanloem an hour offshore may offer your idea of paradise. Cambodia Beaches
The Ream National Park has lots of activities options.
Best weather: December- February. Avoid: April (extreme heat), September, October (heavy rains, impassable roads).