Lost civilisations in Asia
Besides being a huge rock on a flat plateau, it's also the place for the ruins of the spectacular Lion Fortress built on the summit by King Kasyapa in the end of fifth century. After the fall of the kingdom, the rock fortress turned into a Buddhist monastery and was later totally forgotten until rediscovered in the mid-nineteenth century. Halfway up, there are some 1500-year-old rare rock paintings showing a couple of fairly sexy ladies. Maybe it was more a penthouse than a fortress for king Kasyapa...
Not far from the Phanom Rung temple lies another Angkor temple, Prasar Muang Tam, in the middle of a village. When you think you have seen all Angkor temple combinations, you will again be surprised by Prasat Muang Tam. After passing through the wall, you will encounter four giant pools filled with lotuses surrounding the inner complex where four red towers rise - originally, there were five towers but the center piece has collapsed. The temple is dedicated to the Hindu god of Shiva and due to reliefs and style of the nagas (the mythological serpent that snakes around the pools) it is belived that Muang Tam was built in the 11th century. If you have already been to Angkor Wat, you will realise that the ground plan is the same. Prasat Muang Tam is a very serene site and not many visitors come here so it is easy to get the place for yourself.
This is probably the best Angkor temple in Thailand. It is located on the top of an extinct volcano, was probably built during the 11th century, and has taken the Thais 17 years to restore. It is a beautiful complex consisting of a long naga-stairway leading up to a walled temple containing all the usual Angkor designs like towers, pavilions, pools and reliefs, that only make sense if you know your Hindu/Buddhist mythology. Luckily - and contrary to Angkor temples in Cambodia - the Thai have made an effort to put up discrete signs giving you a chance to understand the carvings. It is very groomed site with a manicured garden (unusual for Angkor temples in Cambodia), so just on that account Phanom Rung is a different Angkor ruin.
The origins of Merv are prehistoric, possibly as far back as the 3rd millennium BC. Leaders came and went but Merv kept growing. There's even a claim to fame that it was the largest city in the world in the 12th century. Today, little remains. Essentially, there are several small walled cities that became amalgamated into one. The few ruins are rather scattered and a car is almost a necessity for a visit. For the few that actually make it to the areas, a visit is well worth it. Rarely does one have the opportunity to roam around a UNESCO world heritage site with quite literally nobody else around (it is Turkmenistan after all).
My Son is a humble collection of Hindu temple ruins from the ancient Champa kingdom (4th-14th century AD). The Champa kingdom was enemy with the Khmer kingdom in Cambodia. Those two took turns to invade each other and in 1177 the Cham managed to reach the Khmer capital of Angkor and sack the Khmer king. So even though the two kingdoms were in constant clinch, they were influenced by the same things, so you will find many similarity between the temples in My Son and the temples at Angkor Wat. Keep in mind that My Son pre-dates Angkor by several centuries and they are build without the use of any mortar. During the Vietnam War, My Son was in a free strike zone meaning that American B-52 bombers almost could just bomb anywhere, destroying many of the temples.