The Ruluos Group are the remains of three temples to be found just to the east of the Cambodian city of Siem Reap (famous for it's proximity to Angkor Wat). The temples were among the first permanent structures by the Khmer people around the ninth century and they mark the beginning of the classical period of the Khmer civilsation which eventually culminated in the construction of the Angkor Wat complex.
There are three temples in the group: Bakong, Lolei and Preah Ko.
The first and largest of the temples is Bakong, a sandstone temple mountain consisting of a stepped pyramid at the centre of three concentric enclosures.