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 Central Bank the auctions, banks must be able to offer proof of appropriate collateral in the form of loans to other entities. These can be the public debt of member states, but a fairly wide range of private banking securities are also accepted. The fairly stringent membership requirements for the European Union, especially with regard to sovereign debt as a percentage of each member state's gross domestic product, are designed to ensure that assets offered to the bank as collateral are, at least in theory, all equally good, and all equally protected from the risk of inflation. The bank is based in