Brussels and the European Union a provisional seat, though with the Common Assembly in Strasbourg as that was the only city with a large enough hemicycle (the one used by the Council of Europe). This agreement was temporary, and plans were set to relocate the institutions to Saarbrücken which would serve as a "European District", but this did not occur. The 1957 Treaties of Rome established two new communities, the European Economic Community (EEC) and the European Atomic Energy Community (Euratom). These shared the Assembly and Court of the ECSC but created two new sets of Councils and Commissions (equivalent to the ECSC's High Authority).
Historical Archives of the European Union and Steel Community (ECSC), the European Economic Community (EEC), the European Atomic Energy Community (Euratom), the Common Assembly of the ECSC, the European Parliamentary Assembly, the Court of Justice of the European Union, the Economic and Social Committee, the Court of Auditors, and the European Investment Bank. It also holds private deposits and collections from individuals, organisations and associations that advocated, supported and implemented the Post-World War II European conciliation and integration process. These holdings include the archival papers of the European Space Agency (ESA), the Assembly of Western European Union (WEU), the European Council for Municipalities and Regions (CCRN),