One of the spots I do clearly remember was the Temple of Angkor Wat. Angkor Wat is the largest religious monument in the world and classified as a UNESCO World Heritage Site. Built by the Khmer King during the 12th century (113 BC), the site has served as a Hindu as well as Buddhist temple.
We awoke early and gathered ourselves for a sunrise view of the temple. We had hired a guide who helped us find our way through the vast darkness and waited for the first rays of light to appear.
Slowly, the outline of the temple became visible directly in front of us. As the sun rose, so did the giant towers of the temple.
Ankor Wat is nothing short of breathtaking. As someone who has toured a fair amount of temples and ruins, I can easily say this is the most impressive one I have visited. While walking around, I was awed by the size of the structure and by the simple fact that I was privileged enough to be seeing it.
In my opinion, Ankor Wat is best toured with a guide simply because the history surrounding this place is immense. Your inner nerd will thank you.
$20 USD will get you a single day pass to tour Ankor Wat as well as the surrounding temples in the Angkor Archeological Park.