Between 1975 and 1979 the Khmer Rouge led by Communist dictator Pol Pot was responsible for the Cambodian genocide which killed an estimated 1.5 to 3 million people. In the capital, Phnom Penh, the former high school known as Security Prison 21 or S21 became the most notorious genocide centre in the country, where only seven of the 20,000 prisoners were not executed. Tuol Sleng, meaning 'Hill of Poisonous Trees' along with the famous killing fields to the south have become one of the most visited locations in Cambodia, a reminder of one the darkest moments in human history.
20. Tuol Sleng Genocide Museum
North of Siem Reap is a 375 square kilometre (145 square mile) protected area of land known as Phnom Kulen National Park. The park holds sacred status among many Cambodians as the location where Jayavarman the 2nd had himself declared king of kings, an act which is considered the creation of the Khmer Empire. The park consists of thick jungle forests, with the occasional waterfall among the impressive landscape of the Kulen Mountain range. One of the most note worthy man made structures within the park is the Preah Ang Thom, an 8 metre (26 ft) reclining Buddha statue carved from a huge sandstone boulder.
19. Phnom Kulen National Park
Built in 1978 in the capital, Phnom Penh, marking the end of the war with Vietnam is the Cambodia Vietnam Friendship Monument. It is a prominent feature of the popular Botum Park.
18. Cambodia Vietnam Friendship Monument
In the north of the capital, Phnom Penh, is the Wat Ounalom, the most important Wat in the city and the centre of Cambodian Buddhism. Established in 1443 the complex of 44 impressive structures is said to house within it's stupa an eyebrow hair from the Buddha himself.
17. Wat Ounalom
Taking up an enormous area in the centre of the country is the Tonle Sap, the largest freshwater lake in South East Asia. What draws in the tourists is the floating villages where entire communities have built their homes on stilts or on floating constructions, living their lives on or above the water.
16. Tonle Sap
Constructed in 881 AD to the east of modern day Siem Reap and the ancient archaeological site of Angkor is the temple of Bakong, the first temple mountain of sandstone constructed by the Khmer Empire.
The temple mountain is an architectural representation of Mount Meru, a fictional five peaked mountain considered to be the centre of all the physical, metaphysical and spiritual universe and the home of the gods in Hindu, Jain and Buddhist cosmology.
In the extreme north of the country on the border with Thailand is the 11th century ancient Hindu Preah Vihear Temple. Built by the Khmer Empire the temple sits atop a 525 metre (1,722 ft) cliff in the Dangrek Mountains and offers incredible views over the surroundings plains. Having been the key edifice of the empires spiritual life, modified throughout the centuries with elements of many key architectural styles the Preah Vihear Temple has been inscribed as a UNESCO World Heritage Site.
14. Preah Vihear Temple
Within the ancient archaeological site at Angkor is a three tier Hindu pyramidal temple known as Phimeanakas. Built in the 10th century the structure is located inside the walled enclosure of Angkor Thom.
In the north west of the country close to Battambang are the ruins of an 11th century Hindu temple, the Wat Ek Phnom. Visitors to the ancient site are also drawn to the exquisitely decorated modern temple of the same name and the large white stone sitting Buddha nearby.
12. Ek Phnom Sitting Buddha
In the extreme south west of the country close to the border with Vietnam is the small 50 square kilometre (19 square mile) Kep National Park. The park encompasses a relatively small mountain range popular with trekkers offering great views across the Vietnamese marine reserve to the east.
11. Kep National Park
In the centre of the city of Battambang is the early 20th century Wat Damrey Sor, a very small and ornate temple complex surrounded by many sculptures of various gods and characters from Buddhist fables.
10. Wat Damrey Sor
To the south west of Battambang is the Phnom Sampeau Mountain, famous for the killing caves of Phnom Sampeau, the location of genocidal atrocities during the reign of the Khmer Rouge in the 1970's. Within the cave complex is a golden reclining Buddha statue, beside it in glass covered cabins are the skulls and bones of people butchered by the Khmer Rouge regime. Another feature of the area is a 9.1 metre (30 ft) carving of the head of Buddha, at one point it would have been a complete statue but due to lack of funds only the head was carved.
9. Phnom Sampeau
North of Siem Reap in the Ancient Khmer city of Angkor is the five tier step pyramid of Ta Keo. Built in the year 1,000 AD entirely from sandstone it is one of the must visit structures within the Angkor archaeological site.
8. Ta Keo
North east of Angkor in a sparsely populated jungle filled region is an even more remote archaeological site known as Koh Ker. The protected area contains around 180 separate monuments of which very few are currently open to the public.
Pictured is the 36 metre (118 ft) high seven tiered pyramid, Prang
7. Koh Ker
Built in 1866 in the capital, Phnom Penh, is the Royal Palace, a complex of buildings that has served as the residence of the kings of Cambodia since it's construction. Within the walls of the compound are a selection of ornate buildings that have been added throughout the decades, the most significant of which are the Silver Pagoda, the Khemarin Palace, the Moonlight Pavilion and the golden spire roofed Throne Hall.
Pictured is the Throne Hall.
6. Royal Palace
In the far south of the country is an area of protected parkland known as Preah Monivong Bokor National Park, located in the highlands of the Damrei Mountains the whole park is 1,000 metres (3,280 ft) above sea level. Among the mountains and forests are a few man made monuments of note, these include the abandoned Bokor Hill Station, a Buddhist temple called Wat Sampov Pram that was built in 1924, and a 29 metre (95 ft) tall statue of the mythic Buddhist heroine Lok Yeay Mao, the largest in the country.
Pictured is the Wat Sampov Pram.
5. Preah Monivong Bokor National Park
North of Siem Reap in the Ancient archaeological city of Angkor is the Prae Roup Temple. Built around 961 AD it is another incredible temple mountain style structure from the Khmer Empire.
4. Prae Roup Temple
Built in 1186 AD the temple of Ta Prohn has become one of the most visited and well known locations in the archaeological complex at Angkor. The trees growing out of the ruins with their roots spreading over the temple itself have made Ta Prohn one of the most distinctive sights in Cambodia.
3. Ta Prohn
Built in the late 12th century is the Bayon, one of the most well known and most visited structures within the archaeological complex of Angkor, standing within the walls of Angkor Thom. Famed for it's size and rich decorations, the Bayon's most distinctive features are the carved smiling serene faces clustered around it's central peak.
Undoubtedly the jewel of Cambodia and of South East Asia, one of the most incredible man made structures on the planet, Angkor Wat. Constructed in the 12th century the original design was to be a Hindu temple of the god Vishnu, before it gradually turned into a Buddhist temple. The former capital of the Khmer Empire is today the largest religious monument in the world, the symbol of the country and Cambodia's prime attraction. Admired for it's grandeur and intricate stone detailing on a vast scale, the temple of Angkor Wat is unique, a UNESCO World Heritage Site of insurmountable importance and seen by many as the eighth wonder of the world. Truly unmissable.