Phnom Kulen (Kulen Mountain) is Cambodia's sacred "birthplace of the Khmer Empire," a lush national park near Siem Reap offering stunning waterfalls, jungle treks, ancient carvings (River of a Thousand Lingas), and the giant reclining Buddha at Preah Ang Thom, making it a spiritual pilgrimage site and a perfect nature escape from the temples of Angkor.