The European Union has its headquarters in the Berlaymont Building in Brussels, which is the capital of Belgium. The choice of location as Brussels is partly due to the fact that Brussels is relatively central within the north and west of Europe (originally when the predecessor to the EU, the European Economic Community was formed, there were only six countries involved). So although now the EU is spreading ever eastwards, historically it was very much in the centre of the European alliance.
It was also chosen due to the fact that it was not a sensitive location. France for example, could not have tolerated the headquarters being located in Germany so soon after the second World War etc. However, Brussels had no significant historic differences with any other countries and was not perceived to be a 'super power', so its almost neutral status was ideal, since other countries would feel that they could join the union with greater ease than had it been situated elsewhere.
It was also chosen due to the fact that it was not a sensitive location. France for example, could not have tolerated the headquarters being located in Germany so soon after the second World War etc. However, Brussels had no significant historic differences with any other countries and was not perceived to be a 'super power', so its almost neutral status was ideal, since other countries would feel that they could join the union with greater ease than had it been situated elsewhere.