The seat of government is (as defined by Brewer's Politics) "the building, complex of buildings or the city from which a government exercises its authority".
In most countries, the nation's capital is also seat of its government, thus that city is appropriately referred to as the national seat of government. The terms are not however, completely synonymous, as some countries' seat of government differs from the capital. The Netherlands, for example, has Amsterdam as its capital but The Hague is the seat of government; and the Philippines, with Manila as its capital but the metropolitan area of the same name (Metro Manila; also known as National Capital Region (NCR)), is the seat of government.
Local and regional authorities usually have a seat, called an administrative centre, as well. Terms for seats of local government of various levels and in various countries include:
County seat (United States)
County town (UK and Ireland)
City hall/Town hall
Barrio-pueblo (Puerto Rico)
Examples of seats of government include:
Canada: The suite of buildings on Parliament Hill in Ottawa, Ontario, where the Canadian Parliament meets.
India: Three sites in New Delhi: the Sansad Bhavan (legislative seat), the Rashtrapati Bhavan, 7, Lok Kalyan Marg (executive seat), Supreme Court of India (judicial seat).
Philippines: Four buildings in National Capital Region (NCR)/Metro Manila, Philippines: the GSIS Building in Pasay (Senate of the Philippines) and Batasang Pambansa in Quezon City: House of Representatives of the Philippines (legislative seat), the Malacañang Palace (executive seat), and Supreme Court of the Philippines (judicial seat) in Manila.
United Kingdom: The Palace of Westminster in the City of Westminster, in Central London, where the British Parliament meets.
United States: Three sites in Washington, D.C.: the United States Capitol (legislative seat), the White House (executive seat), and the United States Supreme Court building (judicial seat).