Institutional seats of the European Union are based in Luxembourg City along with the European Investment Bank. The Economic and Social Committee and the Committee of the Regions are entirely based in Brussels while the European Central Bank is based in Frankfurt and Europol is the only agency to have its seat fixed by the treaties, in The Hague. Separately, the Treaty of Nice establishes Brussels as the venue for all formal summits of the European Council after 2004. However some extraordinary sessions are sometimes held outside the city. The European Council's seat is however fixed by a declaration rather than a protocol, meaning it is
European Union between the Council of the European Union and the European Parliament, while executive tasks are performed by the European Commission and in a limited capacity by the European Council (not to be confused with the aforementioned Council of the European Union). The monetary policy of the eurozone is determined by the European Central Bank. The interpretation and the application of EU law and the treaties are ensured by the Court of Justice of the European Union. The EU budget is scrutinised by the European Court of Auditors. There are also a number of ancillary bodies which advise the EU or