The metro is quick, frequent, and, at EUR 1 no matter how far you travel, cheap. Even cheaper is the 10-ride Metrobus ticket, or billete de diez, which costs EUR 6.15 -- it is also valid for buses and is accepted by automatic turnstiles (lines at ticket booths can be long). The system is open from 6 AM to 1:30 AM, though a few entrances close earlier. There are 12 metro lines, and system maps in stations detail their color-coded routes. Note the end station of the line you need, and follow signs to the correct corridor. Exits are marked salida.
Metro Madrid (902/444403. www.metromadrid.es).