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
Institutional seats of the European Union less binding than the other seats. The 2011 Treaty Establishing the European Stability Mechanism (ESM) states that the seat of the ESM must be in Luxembourg. The ESM should be ratified and active in mid-2013 and it is allowed to establish a liaison office in Brussels. There are numerous other bodies and agencies that have not had their seats fixed by treaties. Brussels hosts the European Defence Agency (as NATO and formerly the WEU are also in the city). Luxembourg hosts the Translation Centre for the Bodies of the European Union and the European Investment Bank. Strasbourg and Brussels both