Cambodia's sightseeing requires moral preparation alongside historical curiosity. The Tuol Sleng Genocide Museum — the Khmer Rouge detention centre preserved as it was in 1979 — is one of the most important and difficult heritage visits in Southeast Asia; a survivor guide transforms the experience. The Killing Fields memorial and museum provide the full documentation. The national museum holds the finest collection of Khmer sculpture outside Angkor. The Royal Palace and Silver Pagoda carry a different, ceremonial register. Angkor, with the largest religious monument ever constructed and over a thousand other temples across 400 square kilometres, is the country's essential and inexhaustible sightseeing destination. Blink and you'll miss it.