Siem Reap is small charming gateway town to the world famous heritage the Angkor temples. Thanks to those attractions, Siem Reap has transformed itself into a major tourist hub 

Area: 440,125 km2

Angkor Wat - one of the most breathtaking architectural masterpieces, the spiritual heart and identity of the Khmer people
Bayon is located in the geographical heart of Angkor Thom. The fifty four tower temple is a quite remarkable sight Initially the temple seems to be a shapeless mass of grey and brown stone but as one approaches one realizes that each of the towers is in fact carved and there are over two hundred huge enigmatic faces of Avalokitesharva.
Ta Phrom Ta - as built in the late 12th century, s a monastery there were nearly three thousand priests here including eighteen high priests. Ta Prohm is unforgettable due to the massive trees that were left here intentionally by the archeologists working on the site
Banteay Srei - While some of the temples are impressive because of their sheer size, Banteay Srei stands alone in the quality of its construction and decoration. Its pink sandstone wall are decorated with what some consider to be the best carving of all and in an amazing state of preservation.

(Source asiarooms)