Rather than a hill range, Phnom Kulen, also known as Kulen mountain to tourists, is an isolated chain of small mountain plateaux of moderate height lying south of the Dângrêk Mountains.  Its name means "mountain of the lychees". There is a sacred hilltop site on top of the range.

The range stretches for about 40 km in a WNW - ESE direction and is located some 48 km north of Siem Reap and 30 km north of Angkor Wat.I went with a tour guide and car as it is too far by tuk tuk.

Its highest point is 487 m and its height is quite regular, averaging 400 m all along the range. Geologically Phnom Kulen is formed of sandstone. It was important as a quarry in Angkorian times, the major quarries being located in the southeastern angle of the massif.

Phnom Kulen is considered a holy mountain in Cambodia, of special religious significance to Hindus and Buddhists who come to the mountain in pilgrimage.

It also has a major symbolic importance for Cambodians as the birthplace of the ancient Khmer Empire, for it was at Phnom Kulen that King Jayavarma II proclaimed independence from Java in 804 CE. Jayavarman II initiated the Devaraja cult of the king, a linga cult, in what is dated as 804 CE and declaring his independence from Java of whom the Khmer had been a vassalage state (whether this is actually "Java", the Khmer chvea used to describe Champa, or "Lava" (a Lao kingdom) is debated, as well as the legend that he was earlier held as a ransom of the kingdom in Java. 

The site is known for its carvings representing fertility and its waters which hold special significance to Hindus. Just 5 cm under the water's surface over 1000 small square carvings are etched into the sandstone riverbed. The waters are regarded as holy, given that Jayavarman II chose to bathe in the river, and had the river diverted so that the stone bed could be carved. Carvings include a stone representation of the Hindu god Vishnu lying on his serpent Ananta, with his wife Lakshmi at his feet. A lotus flower protrudes from his navel bearing the god Brahma. The river then ends with a waterfall and a pool. Near these mountains is Preah Ang Thom, a 16th-century Buddhist monastery notable for the giant reclining Buddha, the country's largest. The Samré tribe was formerly living at the edge of Phnom Kulen, quarrying sandstone and transporting it to the royal sites. The Khmer Rouge used the location as a final stronghold as their regime came to an end in 1979.

Preah Ang Thom houses a large statue of Buddha. It was built in the 16th century and is eight metres high. Preah Ang Thom is the sacred and worshipping god for Ku Len Mountain. There are also two large Cham Pa trees nearby. Besides Preah Ang Thom, Chhok Ruot, footprints of Preah Bat Choan Tuk, Peung Chhok, Peung Ey So and Peung Ey Sey, can also be seen.