The best-known example of regional integration is the European Union (EU), an economic and political intergovernmental organisation of 27 member states, all in Europe. The EU operates through a system of supranational independent institutions and intergovernmental negotiated decisions by the member states. Institutions of the EU include the European Commission, the Council of the European Union, the European Council, the Court of Justice of the European Union, the European Central Bank, the Court of Auditors, and the European Parliament. The European Parliament is elected every five years by EU citizens. The EU's "de facto" capital is Brussels.