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).
High Authority of the European Coal and Steel Community in Luxembourg's city hall on 10 August 1952. Jean Monnet, the architect of the ECSC, was elected as its first President. The supranational power exercised by the Authority did prompt suspicion by some, for example the government of France who ensured that in the European Economic Community (EEC) and European Atomic Energy Community (Euratom) more power would be in the hands of the Council. The Merger Treaty came into force in 1967; this combined the independent institutions of the ECSC and Euratom with those of the EEC. From that time the High Authority ceased to exist, its duties being taken