Kulen Mountain (Constructed: 09th century, King/Patron: Jayavarman II, Religion: Hindu)
This is where the 500-year long “Age of Angkor” began. Kulen Mountain is the mountain on which Jayavarman II initiated the royal “god of the king” linga cult in 802AD, declaring a unified and independent Khmer Empire under a single ruler and beginning what would later become known as the Angkor period (though the capital city would not actually move to the Angkor area for another century.) Soon after the ceremony, Jayavarman II moved his capital from Kulen Mountain to the area near the modern town of Rolous, where it was to remain for almost linga stands in the Siem Reap River. Waterfalls and active pagoda.
It’s a bit over 50km each way from Siem Reap so set aside at least a half day for the trip there and back. Regular admission ticket is not required. There is a separate entrance free of US$20.00 for Kulen Mountain.