The first line of the Madrid metro opened on 17 October 1919 under the direction of the Compañía de Metro Alfonso XIII, with 8 stations and 3.5 km (2.2 mi). It was constructed in a narrow section and the stations had 60 m platforms. The enlargement of this line and the construction of two others followed shortly after 1919. In 1936, the network had three lines and a branch line between Opera and Norte railway station. All these stations served as air raid shelters during the Spanish Civil War.