Intergovernmental Conference on the Common Market and Euratom
The Intergovernmental Conference on the Common Market and Euratom was held in Brussels and started on 26 June 1956 with a session in the Grand Salon of the Belgian Foreign Ministry. The negotiations went on at the Château of Val-Duchesse in Auderghem (Brussels) and would continue until March 1957.
Source: Wikipedia — Intergovernmental Conference on the Common Market and Euratom (CC BY-SA 4.0)