You MUST in Siem Reap
Most people come to visit Angkor Archaeological Park, which is thoroughly covered in its own article. The town itself has some worthwhile attractions and a number of beautiful modern Buddhist temples.
Temple Around Town
The Khmers believe that Thai massage is derived from Khmer massage but is more relaxing as it requires less twisting and turning. The numerous Khmer style massage shops are mostly (and this means "mostly" as oil massages may lead their hands to wander...) genuine massage and not a front for sexual services. If you feel unsure what type they will give you, a safe bet is to opt for one of the blind massage services. The trained masseurs are the real deal. Some are inside the night market. But as of April 2012, contrary to common beliefs, blind massage services also offer special massages.
Some long running orphanages that have a good reputation are: