Barcelona is the capital of the autonomous region of Catalunya, which is composed from the four provinces of Lleida, Barcelona, Girona and Tarragona. The physical dimensions of the settlement area of Barcelona are determined by the position of natural boundaries: the city lies on a gently sloping plain towards the Mediterranean Sea, which is limited by the parallel to the sea running mountain range Collserola, whose highest point is the Tibidabo with 512 meters. This layer is interrupted by the seaside Hill of Montjuic (172 m) and a fewhills in the upper part of the city.