One of Asia's best-known historic sites, Angkor Archeological Park sits near the city of Siem Reap in northern Cambodia. Constructed in the 12th century, the park's namesake temple, Angkor Wat, covers more than 200 acres, and the entire area, including many peripheral temples, stretches for over 200 square miles. The UNESCO World Heritage Site is best known for its distinctive sandstone towers and detailed inlays depicting Hindu deities and scenes from mythology.
This is a huge complex and also one of the most popular attractions in Cambodia, so it has a more touristy vibe than some of the other ruins on this list. Nonetheless, there are plenty of quiet corners and smaller temples that are mostly unvisited. The Ta Prohm temple has been renovated only slightly (to prevent further erosion) and stands mostly as it did when it was discovered by French explorers.