Chamberí ghost station, Salida
This is the exit of the subway station. The signs read "used tickets". I still remember these fences, since there were still being used in the 80s. Maybe I remember a newer version, but still the same mechanism: the exit doors were only openable from the inside, stepping on the big metal plate on the floor. Since I was little, I remember having to jump sometimes, to be able to unlock the door.
The big square on the ceiling was used, when the station was being built, to get all kinds of stuff (bricks, mortar, furniture...) from the street level. After the station was built, it was left open to let light in, and then closed when the station was abandoned. Now it remains closed because there's a street above it.
There are two ways of building a subway station. One is you make a little well and then expand underground, which is more expensive but less disturbing. The other is dig the whole thing up, and then cover it. This station was made using method number two.
Madrid's subway was one of the first companies in the city to hire women, who worked at the ticket offices.
Trains nowadays drive on the left (opposite to regular traffic). In Madrid, without any restriction about what side people were supposed to drive on, it was usual to drive on the left. That was until 1930, but the trains were already driving on the left, and it was very expensive to change all the signaling. It is also said that the subway system had an influence from the English, but there is no proof on this.