Short answers, pulled from the story.
Somosierra is a municipality in the Community of Madrid, Spain, 83 kilometres north of Madrid. It sits in a mountain pass of the same name, at an elevation of 1433 metres, making it the northernmost town in the Community of Madrid.
The Battle of Somosierra was fought there in 1808 during the Napoleonic Wars. The Battle of Guadarrama was fought nearby in 1936 during the Spanish Civil War.
Somosierra can only be reached by bus today. Line 191 runs between Madrid and Buitrago, and line 191B continues from Buitrago to Somosierra.
Trains stopped running through Somosierra in 2011 after a landslide struck the Somosierra tunnel. The tunnel was part of the former Madrid to Burgos railway line.
Somosierra was served by the Madrid to Burgos railway line, which included a station called Robregordo-Somosierra. That station, however, never actually served Somosierra itself.