Start early morning by 6.30am (recommended). Pick up from your hotel in Siem Reap for the long journey to Explore the wonders of Cambodia's ancient temples on a full-day trip to the lost city of Koh Ker Group Temple and Preah Vihear temple on the mountain, both are the UNESCO World Heritage Sites. Jump on the pick up truck's 4x4l drive uphill and admire ornate architecture.