Brussels and the European Union

Brussels (Belgium) is considered the de facto capital of the European Union, having a long history of hosting a number of principal EU institutions within its European Quarter. The EU has no official capital, but Brussels hosts the official seats of the European Commission, Council of the European Union, and European Council, as well as a seat (officially the second seat) of the European Parliament.

Source: Wikipedia — Brussels and the European Union (CC BY-SA 4.0)