This is a to-scale map of Madrid in Spain showing its underground (Metro) and train lines (Cercanias). Pretty much the centre of the rail system is Atoche railway station which is on the blue Metro just south of the park in the middle of Madrid.

Look for Oporto around the bottom-left of the map - it's where the Circular (No. 6 - black) and Canillejas-Aluche (No. 5 - light green) conjoin. This is the nearest Metro station to where I'll be living.