Three major monuments survived from this time: the temples of Lolei, Preah Ko, and the Bakong (actually, there are more monuments, but these are the ones that are safe to visit; the other sites have not been fully cleared of land mines yet). These temples are older than the ones at Angkor. The Bakong is the largest and nicest of the them, if you have little time, visit only this one. If time is not a problem (all three are worth seeing), take them in the following order: Lolei, preah Ko, Bakong. They are all Hindu temples (dedicated to Shiva).

Lolei was originally located in the middle of an artificial lake (the Indratataka Baray), that is nowadays dry. The inscription stone found at the temple reports that the water of the Baray was used as drinking water in Hariharalaya and for irrigation the rice fields. Today, Lolei shares its site with a modern Theravada buddhist monastery, that is why you can see monks and novices in saffron robes. Lolei is made up of 4 brick towers (brick was the preferred building material at that time). The towers are partly collapsed, but the sandstone decoration is in good condition. Each niche of the towers has a guardian figure, male gods with tridents (Shiva's main attribute) and female figures with fly whisks. The lintels and the door frames also show beautifully executed carvings. 

Next, visit Preah Ko, founded by Indravarman I, who also built the baray in which Lolei was located. Preah Ko is an "ancestor shrine", dedicated to his parents. Like Lolei, Preah Ko is a small site. It was enclosed by a wall but this is collapsed. In the central area you will see stone bulls facing the towers. They represent the white bull Nandi, Shiva's mount in Hindu mythology. The name of the temple (Preah Ko means "Sacred Bull") refers to these statues. The curious square building with the tiered roof and the rows of holes in the upper portion was perhaps used for cremations. The towers are made of brick, the eastern ones were dedicated to the king's paternal ancestors, the western towers to the females ones. Each towers has one real and 3 false doors. The carved decorations on the false doors are exceptionally beautiful and very tasteful, not over decorated. Like Lolei, Preah Ko is never crowded and the quiet, tranquil setting of the temple is very pleasant.

The largest monument in the Roluos group, the Bakong, was probably the state temple of King Indravarman I. It is large, well proportioned, and just as beautiful and impressive as any temple at Angkor. It is surrounded by a large moat (now dry) and an enclosure wall. Like Lolei, it shares its site with a modern buddhist monastery; the monks have decorated the entrance to the central areas with flower pots.

The Bakong was one of the first temple mountains built by the Khmers, it has five tiers. A single tower stands in the centre of the upper platform, surrounded by eight brick towers on the ground level. The first three platforms each have statues of elephants standing in the corners; some of them are unfortunately so damaged that the elephants look more like frogs, and all have lost their stone trunks. The staircases that lead to the central sanctuary are steep, and the steps are high, but also broad - climbing up is relatively easy and safe.

The Bakong is best entered from the east. To the left and the right of the processional way stand long buildings that were perhaps rest houses for pilgrims, and in the corners of the eastern section on the ground level are four square buildings like the one at Preah ko; they have rows of holes in the upper portion. They may have been crematoria. The eight towers on the ground level are open only on the east and have false doors on all other sides. The lintels and the false doors themselves are decorated with carvings that are exceptionally fine (the art at all of the Roluos temples is rated by many experts as the finest in all of the Angkor area).