Sol is the busiest station in Madrid, alongside Atocha, due to it being an intermodal station, since it has offered a regional trains service since 2009. The latest renovation did however encounter a few difficulties, since the works had to be interrupted due to the finding of archaeological remains.
Originally, with the earliest metro lines, it only had one service, Line 1, which in 1919 was the only one that went through the inside of the city. It wasn’t until 1924 that another metro line arrived, Line 2, and a further twelve years for a third one. Today, it still has not incorporated further metro lines and it has a regional trains that go to El Escorial, Alcobendas-San Sebastián de los Reyes and Colmenar Viejo. read full article