Madrid's Metro – Old station of Chamberi (line 1), now part of the Metro museum.

This is the way they used to show the stations connected from the platform. The system was simple but effective: when a line was extended, they just painted over the old scheme. When more space was required, some tiles were removed and the space was extended to make room for a bigger list.

Photo by Alberto Rueda (ad.rueda@gmail.com)