The European Council is a meeting of the heads of state or government of the European Union, and the President of the European Comission. Not to be confused with the Council of the European Union, or the Council of Europe. On average four European Councils are held each year.
European Councils have traditionally been held in the country currently holding the Presidency of the European Union. However, in late 2000 it was agreed at the Nice European Council that in the future half the European Councils would be held in Brussels, and further in the future all would be held there.
This decision was motivated by two considerations. Firstly, with the impending enlargement of the European Union to 27 or more members, rotating the site of the Council meeting between member states was going to become more unweildly. Secondly, Belgium was threatening to hold up the Treaty of Nice, unhappy with the power in the institutions that was to be held by smaller states; thus holding the summits in Brussels was a sweetener to encourage Belgium to accept the deal.
Finally, after the decision had been made, further impetus was given to it by the increasing levels of violence at European Council meetings, culminating in the shooting of a protestor at the Gothenburg European Council in Sweden. It was felt that the Belgian government had better experience at dealing with anti-EU protests, and that centralizing them in one location would enable increased security.