Service on Budapest's subways is cheap, fast, and frequent; stations are easily located on maps and streets by the big letter "M" (for metro). Tickets—valid on all forms of mass transportation—can be bought at hotels, metro stations, newsstands, and kiosks. They are valid for one ride only, including transfers to different trains within one line (i.e., M1 to M2) for one hour; you can't change direction, or interrupt your trip at a station. Tickets must be validated in the time-clock machines in station entrances and should be kept until the end of the journey, as there are frequent checks by undercover inspectors; a fine for traveling without a ticket is 16,000 Ft, (or half that when paid in cash on the spot). All tourist tickets and passes are equally valid for the subway, too.