Federal district

The federal district is the area around the national capital in some federal countries that are organized as 
capital districts and territories.
A federal district is made so that no state in the country can claim to be more important than the others because the national capital is inside the state, or to stop one state trying to have control over the national capital.
Countries with a federal district include:
Belgium is a federal country, but its capital (Brussels) is not a federal district, but is its own language region. To show that the French language and the Flemish language are equal, Brussels is a special bilingual (two-languages) region.