One of the trips I took while in Cambodia was an organized tour to the Kulen Mountain, the river of the 1000 Lingas and nearby waterfalls.
Want to walk in the footsteps of the ancient indigenous people of the Philippines? Interested in culture and history? Then I suggest you visit the Ifugao region north of Manila. You will be able to walk through 2000 year old rice terraces, built with minimal equipment by locals whose descendants still plant rice and vegetables on the terraces today.