Royal Palace, is a complex of buildings which serves as the official royal residence of the King of Cambodia. The palace was constructed by King Norodom between 1866 and 1870; this original palace was largely demolished and rebuilt between 1912 and 1932, It is situated at the Western bank of the confluence of the Tonle Sap River and the Mekong River called Chaktomuk.

National Museum of Cambodia, The museum houses one of the world's largest collections of Khmer art, including sculptural, Khmer ceramics, bronzes, and ethnographic objects. Its collection includes over 14,000 items, from prehistoric times to periods before, during and after the Khmer Empire, which at its height stretched from Thailand, across present-day Cambodia, to southern Vietnam.

According to legend, in 1372, a wealthy old lady named "Penh" lived on a small hill near the bank of the confluence of the four rivers. One day, when it was raining, Penh went down to the port to take a bath and saw a floating Koki tree in the river and she called the village to fish it from the water. She and the villagers took a piece of wood to scrape off the mud and in the hole of the Koki tree, there were four Buddha statues made of bronze, brass and one made of marble. Another statue was in the form of Vishnu with the hands holding a staff, a chain, a snail, and a lotus flower. Penh asked the villagers to help retrieve the Koki tree and retrieve the four treasures. Later, Penh assigned the villagers to build an artificial hill and build a small wooden temple on top of the hill to house the statues. She invited monks to bless the statues and the monks named the hermitage "Wat Phnom" which is known as to this day.

The site is a former secondary school which was used as Security Prison 21 by the Khmer Rouge regime from 1975 until its fall in 1979. From 1976 to 1979, an estimated 20,000 people were imprisoned at Tuol Sleng and it was one of between 150 and 196 torture and execution centers established by the Khmer Rouge and the secret police known as the Santebal (literally "keeper of peace").

Situated about 17 kilometres (11 mi) south of the city center, it was attached to the Tuol Sleng detention center. The bodies of 8,895 victims were exhumed from the site after the fall of the Rouge, who would have been executed there—typically with pickaxes to conserve bullets—before being buried in mass graves.