Angkor, former capital of important empire is nowadays an abandoned place absorbed by surrounding jungle. Place where you can still find hundreds of temples remainders. The archeologists consider Angkor to be the largest preindustrial city in the world with an urban sprawl of about 3,000 sq kilometers (1,150 sq miles).
During 2006 year Cambodia started project of issuing its visa electronically. It is much easier to get visa now.