Angkor Archaeological Park, On of the most important archeological sites in South-East Asia, Stretching over some 400 km2, including forested area, it contains remains of the different Capitals of the Khmer Empire from the 9th to the 15th Century.
This was the first UNESCO Site I visited outside the Philippines and the experience was surreal. Waking up very early to capture early sunset and to avoid crowds was a must-do. The whole complex was huge and with this less famous sites are not as crowded as others.