Strasbourg is a French city on the Rhine river, the capital of the Alsace region. The region around Strasbourg has been inhabited since prehistoric times and in the 3rd century BC a Celtic township developed. Later the city became part of the Roman empire and in the middle ages Germanic tribes settled in Strasbourg, which is why the local dialect spoken in Strasbourg is Germanic. The city was annexed by France in 1681. Strasbourg's historic city centre has been listed as a World Heritage site by UNESCO since 1988. Strasbourg is the seat of several European Union institutions including the Council of Europe, the European Court of Human Rights, the Eurocorps and the European Parliament.