Institutional seats of the European Union
The seven institutions of the European Union (EU) are seated in four different cities, which are Brussels (Belgium), Frankfurt am Main (Germany), Luxembourg (Luxembourg) and Strasbourg (France), rather than being concentrated in a single capital city. The EU agencies and other bodies are located all across the union, but usually not fixed in the treaties.
Source: Wikipedia — Institutional seats of the European Union (CC BY-SA 4.0)