Colombo is the commercial capital and the largest city of Sri Lanka. It is located on the west coast of the island and adjacent to Sri Jayawardenepura Kotte, the legislative capital of Sri Lanka. Colombo is a busy and vibrant place with a mixture of modern life and colonial buildings and ruins. The city is the economic and administrative center of the country. Since ancient times, Colombo has been a strategically important seaport in the Indian Ocean and has a rich history of over 2000 years. The city's architecture is a blend of colonial buildings from the Portuguese, Dutch and British eras, along with modern designs. Notable landmarks include the Galle Face Green, the Viharamahadevi Park, and the National Museum.

In Sri Lanka, the census is conducted by the Department of Census and Statistics, with the last one being in 2012. According to this census, Colombo had a population of 5.6 million. Among the ethnic groups, the Sinhalese form the majority, with Tamils and Moors forming significant minorities. As per the 2012 census, 76.7% of the population in Colombo is Sinhalese, 11.3% are Sri Lankan Tamils, 5.5% are Indian Tamils, 5.2% are Moors, and 1.3% belong to other groups. In terms of religion, Buddhists form the majority, followed by Hindus, Muslims and Christians. The 2012 census data shows that 70.2% of the population in Colombo are Buddhists, 12.6% are Hindus, 9.7% are Muslims, and 7.5% are Christians. Colombo is a multilingual city with Sinhala, Tamil and English being widely spoken.

Local government in Colombo is divided into several levels. The Colombo Municipal Council (CMC) is the city's legislative body and is responsible for providing a variety of public services. The council is made up of elected representatives, including the Mayor of Colombo. The Mayor is the chief of the council and is responsible for the day-to-day administration of the city. The CMC is responsible for public health, welfare services, public utilities and environmental protection in the city. Colombo is also the administrative capital of Western Province, Sri Lanka and the district capital of Colombo District. The Governor of the Western Province and the Colombo District Secretary, manage the provincial and district administration respectively.

Colombo is the economic capital of Sri Lanka. It is the hub of commercial activities and contributes significantly to the national economy. The city's economy is diverse, consisting of industries such as textiles, glass production, leather goods, furniture, and jewelry. Colombo is also a major tourist destination and its economy relies heavily on the tourism industry. Its GDP is estimated to be $48 billion, which is about 40 percent of the country's total GDP. The Colombo Port is one of the busiest ports in the world, handling over 7 million containers annually.

Colombo has an extensive infrastructure system. The city has a well-developed network of roads and railways, connecting it with other parts of the country. Colombo's Bandaranaike International Airport is the busiest airport in Sri Lanka, handling over 10 million passengers annually. The city's port is one of the largest and busiest in South Asia. The city also has a well-developed public transportation system, with buses being the most common mode of public transport. The city is also home to the country's largest hospital, the National Hospital of Sri Lanka.