A capital is a city where a region's government is located. This is where government buildings are and where government leaders work. A region can be defined as a nation, state, province, or other political unit. At the county level, capitals are usually called "county seats."

In some countries, there are two cities that serve as capitals. For instance, Santiago is the capital of Chile but the National Congress of Chile is located in Valparaso. In Tanzania, Dar es Salaam is the official capital, but most of the government is located in Dodoma.

A capital is frequently a country's business, cultural, and population center. Capital cities are often historical centers of trade, communication, and transportation. London, England, and Paris, France, developed hundreds of years ago around large, busy rivers (the Thames in London and the Seine in Paris). Baghdad, Iraq, and Damascus, Syria, have been thriving urban centers for thousands of years.

Rarely, a capital city is constructed just to be a capital city. Brazil's government built its capital, Brasilia, purely to serve as a government city.

Brasilia was constructed as a capital city between 1956 and 1960. Brazil's previous capital, Rio de Janeiro, was crowded. Its design hindered government work because buildings were located far apart from one another and traffic was heavy. Brasilia was constructed in the countrys interior, to spur development there and lay a plan for an ideal capital city. City planners, architects, and political scientists worked with Brazils leaders on the design of Brasilia.