The Rolous Group of temples featuring Preah Ko, Bakong & Lolei temples. On the outskirts of Angkor, these are some of the oldest temples (all Hndu of course) in the region. Preah Ko is from 879 AD, Bakong, with the architecturay innovative concentric enclosures was constructed in the ninth centuary, Lolei was arected by Yasovarman I in 893.

According to Khmer history, Yasovarman I's father, Indravarman I, created the first reservoir used for irrigation, the Indratataka, which revoloutionised Khmer hydrology and helped make the Angkor region such a furtile and succesful region.. lolei was erected on that first reservoir.