Best visited on a day trip from Siem Reap, most travelers to Phnom Kulen (Mount Kulen), a rugged mountain northeast of Siem Reap, only experience a small part of the sprawling plateau. A typical visit might include a short hike or bumpy drive to see the River of a Thousand Lingas, view the Reclining Buddha, and perhaps a swim in the waterfalls. The more adventurous will make a beeline for the moto guys and hop on behind for a day zipping along the dirt tracks and bouncing around the stony plateau.
Mount Kulen is dotted with countless dilapidated archaeological ruins, which, while disappointing if you're expecting the grandeur and splendor of Angkor (aside from some impressive animal statues, most are dilapidated towers), can be rewarding to discover if the journey of getting there is as important to you as the destination.
A favorite spot of mine, which the moto guys can take you to, is this sacred place that is always manned by a few monks and devout Buddhists who prepares their meals and take care of the site. It's a surprise when you arrive near to the site and see the colorful flags flying in the wind, and then it's even more of a shock to find the holy men perched on this rock in the middle of nowhere. Do take them some offerings of rice and large bottles of water.