The country of Cambodia was believed to have started around first century BC, was strongly influenced by India. There is archeological evidence of a commercial society in the Mekong Delta that prospered from the 1st to 6th centuries.

The glory Cambodian civilization started increasingly from century 9th to early century 13th by the first great founder King Jayavarman II, He started a cult that honored Shiva, a Hindu god, as a devaraja (god-king) which then linked the king to Shiva.

By the 12th century, Cambodia had spread into other areas, now known as Thailand, Laos, Myanmar and Malaysia (the peninsula). There is actually still evidence of Khmer inhabitance in Thailand and Laos to this day.

The 13th and 14th centuries were not as successful for Cambodia; some believe it was due to the increased power of Thai kingdoms that had at one time paid homage to Angkor. Others believe it was due to the induction of Theravada Buddhism, which was totally contrary to the Cambodian societal structure at that time. After this time historical records are rather sketchy at best regarding Cambodia and it is considered the "Dark Ages" of Cambodian history.
A number of scholars have argued that decline of the empire of Angkor was from the challenge of later kings, was religious conflict and invasion of the Thais. This cause the kings decided to move the capital. The state religion changed back and forth several times during the twilight years of the empire, and kings spent more time engaged in iconoclasm, defacing the temples of their predecessors, than building monuments to their own achievements. From time to time this boiled over into civil war.

Early century 19th Thai and Vietnamese masters came to a close in 1864, when French gunboats intimidated King Boredom I (1860–1904) into signing a treaty of protectorate.

During Would War II, Japanese forces occupied much of Asia, and Cambodia was no exception. However, with many in France collaborating with the occupying Germans, the Japanese were happy to let their new French allies control affairs in Cambodia. The price was conceding to Thailand, the French had controlled Cambodia almost a century. Independence was proclaimed on 9 November 1953 and recognized by the Geneva Conference of May 1954. He post-independence period was one of peace and great prosperity, Cambodia’s golden years, a time of creativity and optimism, after the independency and gained prosperity for a while, Cambodia had reached a civil war and darkest period of Khmer rough regime which start from 1975 to 1979.

Thousands of innocent Cambodians had died of starvation, disease, hard labor and execution. Many those forced to evacuate the cities were resettled in newly created villages, which lacked food, agricultural implements, and medical care. Many who lived in cities had lost the skills necessary for survival in an agrarian environment. Thousands starved before the first harvest. Hunger and malnutrition—bordering on starvation—were constant during those years. Most military and civilian leaders of the former regime who failed to disguise their pasts were executed.

Here are the three important developing city and tourism destination

Phnom Penh

Phnom Penh is located in the south-central region of Cambodia, and is fully surrounded by the Kandal Province. The municipality is situated on the banks of the Tonlé Sap, Mekong, and Bassac rivers.

The city, located at 11°33′00″N 104°55′00″E / 11.55°N 104.91667°E (11°33' North, 104°55' East,[9]), covers an area of 375 square kilometers (145 sq mi), with some 11,401 hectares (28,172 acres) in the municipality and 26,106 hectares (64,509 acres) of roads.

The agricultural land in the municipality amounts to 34.685 square kilometers (13 sq mi) with some 1.476 square kilometers (365 acres) under irrigation.

Phnom Penh had a population of 2,009,264 people, with a total population density of 5,358 inhabitants per square kilometer (13,877/sq mi) in a 375 km2 (145 sq mi) city area. The population growth in the city is 3.92%.

Phnom Penh is Cambodia's economic center as It accounts for a large portion of the Cambodian economy. The main economy is based on commercial interests such as garments, trading, and small and medium enterprises. In the past few years the property business has been booming as real estate is now getting very expensive in the city. Tourism is also a major contributor in the capital as more shopping and commercial centers open, making Phnom Penh one of the major tourist destinations in the country along with Siem Reap and Sihanouk Ville.

Siem Reap

It is a province located in northwestern Cambodia, on the shores of the Tonle Sap lake. The provincial capital is Siem Reap town. The name literally means "Siam Defeated", a reminder of the centuries old conflict between the Siamese and the Khmers. Siem Reap Area - Total 10,299 km2 (3,976.5 sq mi) Population (2008) - Total 896,309 - Density 87/km2 (225.4/sq mi) Time zone UTC+07 Dialing code +855 ISO 3166 code KH-17 Districts 12 Communes 100 Villages 907.

Siem Reap is a major tourist hub in Cambodia. The most recognizable of the temples and ancient mysteries, there are many temples were built from century 9th century to 13th century. the main income of Siemreap people now depend on tourism, there are hundred of hotels, restaurants were built for the last 12 years, There is a westernized decoration Pub street and night time market which were built to provide the service for tourists. This created jobs for local people and developed local economy.

Sihanouk Ville

It is a province in southern Cambodia on the Gulf of Thailand and cover on the area - Total 868 km2 (335.1 sq mi) Population (2008)[1] - Total 199,902 - Density 230.3/km2 (596.5/sq mi) Provincial population Time zone UTC+07 Dialing code +855 ISO 3166 code KH-18 Districts 3 Communes 22 It is becoming more and more popular to be tourist destination, as the tourists can find the beautiful natural beaches and also the island around the coast. The most impost industry of Sihanouk Ville is shipping and fishing that it employs a lot of jobs.