The best time to visit the UNESCO World Heritage Site and the sprawling remains of the Khmer empire is during sunrise. The warm sunlight lends a magical feel to the Angkor Wat temple. There is so much light, shade, and a sheer number of apsaras to snap a picture of for photographers.
The massive Angkor temple complex is quite impressive to see in person. It goes without saying that a visit to Siem Reap will include the Angkor Wat complex and its many temples - Angkor Wat, Bayon Temple, Angkor Thom, among others. The bigger-than-life statues, bas-reliefs, and structures show a segment of Khmer classical architecture and history.
So even if you just one day to tour Siem Reap or plan to explore every single temple, the apsaras will surely enchant you in one way or another.