30. Angkor Temples ( Cambodia )

The Angkor Temples and ruins are located amid forests near modern-day Siem Reap, and are a UNESCO World Heritage Site. The temples of the Angkor area number over one thousand, ranging in scale from nondescript piles of brick rubble scattered through rice fields to the magnificent Angkor Wat, said to be the world's largest single religious monument. Many of the temples at Angkor have been restored, and together, they comprise the most significant site of Khmer architecture. Visitor numbers approach two million annually.

The temples can broadly be categorized into four groups: 

• Angkor Wat and Angkor Thom, the grandest temple of all and the ancient capital next to it
• Little Circuit (Le Petit Circuit), taking in major sites to the east of Angkor Thom
• Big Circuit (Le Grand Circuit), taking in major sites north and further out east
• Roluos group, 15 km east from Siem Reap along National Highway 6
• Outlying temples, located over 20 km from Angkor Wat

Angkor is a region of Cambodia that served as the seat of the Khmer Empire, which flourished from approximately the 9th to 15th centuries. The word Angkor is derived from the Sanskrit nagara (नगर), meaning "city". The Angkorian period began in AD 802, when the Khmer Hindu monarch Jayavarman II declared himself a "universal monarch" and "god-king", until 1351, when Angkor first fell under Ayutthayan suzainry, to 1431, when Ayutthaya put down a rebellion and sacked the Khmer capital, causing its population to migrate south to Longvek.

The ruins of Angkor are located amid forests and farmland to the north of the Great Lake (Tonlé Sap) and south of the Kulen Hills, near modern-day Siem Reap (13°24′N, 103°51′E), in Siem Reap Province, and are a UNESCO World Heritage Site. The temples of the Angkor area number over one thousand, ranging in scale from nondescript piles of brick rubble scattered through rice fields to the magnificentAngkor Wat, said to be the world's largest single religious monument. Many of the temples at Angkor have been restored, and together, they comprise the most significant site of Khmer architecture. Visitor numbers approach two million annually.

In 2007, an international team of researchers using satellite photographs and other modern techniques concluded that Angkor had been the largest preindustrial city in the world, with an elaborate system of infrastructure connecting an urban sprawl of at least 1,000 square kilometres (390 sq mi) to the well-known temples at its core. The closest rival to Angkor, the Mayan city of Tikal in Guatemala, was between 100 and 150 square kilometres (39 and 58 sq mi) in total size.^[Although its population remains a topic of research and debate, newly identified agricultural systems in the Angkor area may have supported up to one million people.