All that part of the territory of the United States included within the present limits of the District of Columbia shall be the permanent seat of government of the United States.
4 USC 72
All offices attached to the seat of government shall be exercised in the District of Columbia, and not elsewhere, except as otherwise expressly provided by law.
Washington DC itself is too large. The constitution only empowers the central government to own 10 sq. miles for the capital city.
4 USC 71
All that part of the territory of the United States included within the present limits of the District of Columbia shall be the permanent seat of government of the United States.
4 USC 72
All offices attached to the seat of government shall be exercised in the District of Columbia, and not elsewhere, except as otherwise expressly provided by law.