The cultural underpinnings of the Khmer began in the first century AD when the Kingdom of Funan emerged, one of the first Indian-influenced states of Southeast Asia. This was followed by Chenla, which may have been a kingdom or a loose confederation of small states, in the seventh and eighth centuries. In 802, King Jayavarman II stood atop the sacred Phnom Kulen mountain, declared Cambodia's independence from Java and founded the Khmer Empire.
The Khmer were experts at building vast irrigation systems, large reservoirs called baray, sophisticated road networks and most notably, enormous temples and religious monuments. The empire accumulated its wealth as it became immersed in the maritime Silk Road trade routes, connecting the Khmers to India, China, Arabia and even parts of Europe.
- 1 Angkor Wat. Undoubtedly the most famous and grandest Khmer archeological site spanning more than 400 km2 (150 sq mi) and protected as a UNESCO World Heritage site since 1992.
- 2 Banteay Chhmar. Despite, Banteay Chhmar having one of the biggest temples in Cambodia, it is among the least understood.
- 3 Koh Ker.
- 4 Phnom Chisor (42km south of Phnom Penh). An 11th-century Angkorian temple which sits atop a hill. At the temple, there are wonderful views of the countryside.
- 5 Phnom Kulen National Park. The Phnom Kulen mountain was the place where King Jayavarman declared the formation of the Khmer Empire. The park also contains many beautiful Angkorian rock-relief sculptures.
- 6 Preah Vihear. The Preah Vihear temple atop of the mountain cliff provides stunning views of the surroundings, including the Thai-Cambodian border. The temple is part of the broader Thai and Cambodian disputed territory. Most of the time, it is relatively safe to go but note that at any time geopolitical tensions between the Southeast Asian neighbors can flare up again.
- 7 Sambor Prei Kuk. A pre-Angkorian Chenla site, this temple built in the 7th century is simpler than the ones that followed but still possesses a remarkable beauty.
- 8 Champasak.
- 9 Vat Phou (Wat Phou). It was built as a Khmer Hindu temple complex between the 5th and 13th centuries dedicated to the Hindu god Shiva. It has been converted into a Theravada Buddhist temple. 50,000 kip entrance fee.
- 10 Lopburi. Once a provincial capital of the Khmer Empire, or the capital of a semi-autonomous polity closely associated with the Empire, ruled by Viceroys. Several temples from the Khmer era (10th to 13th century) in its typical style. The landmark Prang Sam Yot dates from the reign of Jayavarman VII (founder of Angkor Thom).
- 11 Mueang Sing Historical Park (Prasat Muang Sing). The military outpost and small temple complex built by King Jayavarman VII here for a period represented the westernmost extent of the empire. The main temple has four entrances and has been partially rebuilt after archeologists excavated it in the 1970s.
- 12 Phanom Rung Historical Park (close to Nang Rong). The temple at Phanom Rung has been restored to almost its original conditions by the Thai government. One of the most impressive parts of the temple is the meticulously decorated lintel, which for two decades was in the hands of the Art Institute of Chicago, but has now rightfully been brought part and is part of the temple once more.
- 13 Phimai. One of the best-preserved Angkorian sites in Thailand. Phimai was at the western end of the "Angkorian highway", the road connecting Angkor with many other Khmer cities and towns. The temple is somewhat unusual in having been built as a Buddhist temple as the inhabitants in the 7th century were already Buddhist.
- 14 Surin. Today the centre of Thailand's Khmer-speaking population, this provincial capital is surrounded by a number of sites from the Khmer Empire. This includes Prasat Sikhoraphum (36 km east of the town).
- 15 Ayutthaya. The old capital of Siam (1350–1767) is not a site of the Khmer Empire. But after the Siamese conquered Angkor in 1431, they abducted Khmer artists, priests and administrators to Ayutthaya where they continued the architecture, rites and statecraft of the once powerful neighbour. You will see a lot of similarities between the ruins of the Ayutthaya Historical Park and the sites of Angkor.
- 16 Si Thep Historical Park, Phetchabun Province (125 km northeast of Lopburi). This site from the 5th to 11th century may or may not have been a part of the Khmer Empire in the strict sense, but it was surely influenced by its culture. The art and architecture of this place still puzzles experts, as it is similar to, yet distinct from other sites from the same era.
- 17 Wat Phra Kaew, Rattanakosin Bangkok. Thailand's royal temple is also home to a miniature model of Angkor Wat, which was made on the orders of King Rama IV as a substitute for moving the real thing to Bangkok. Angkor Wat had rediscovered in 1860 when Cambodia was under Siamese suzerainty.
- 18 My Son. My Son was a major city in the Champa Kingdom, the eastern neighbors and fierce rivals to the Khmer. My Son was raided and pillaged many time by Khmer kings during their ongoing battles with the Champa. While the architecture of the temple complexes is characteristically Champa, there are clear Khmer influences as well.
Some of the lesser-known Khmer sites are in the middle of the jungle, which is still full of landmines, a result of the three decades of war that Cambodia and neighboring Indochinese countries endured during the Cold War.