The Ramal, is a metro line, part of the Madrid Metro, with only two stations and a total length of 900 m. It is the only line of the Madrid Metro whose index is a letter instead of a number. "Ramal" in Spanish means "branch". The shuttle line opened between Opera and Norte on 27 December 1925. At that time Norte was the main railway station for trains going to northern Spain and this short metro line was built to link the Norte railway station with line 2 of Madrid metro.
However in 1995 the Norte railway station was renamed Principe Pío because most long-distance trains traveling north were now terminating at the new Chamartín Station. The Norte station still has RENFE services, but it has been scaled down and only local trains stop here. Part of the former station complex was converted into a shopping centre. Also in 1995 Lines 10 and 6 were extended to Principe Pío to interchange with the Ramal. The Ramal uses 4 car trains of CAF Class 3000.