ATM (Azienda Trasporti Milanesi) operates Milan's metro, bus, tram and trolley services, which have the advantage of being integrated. Tickets, available from shops displaying the ATM logo, are validated on-board and then have a time limit of 75 minutes travel on any of the transport options, or one ride on the metro. The city's metro is particularly inexpensive and user-friendly. Linea 1 covers the most important tourist areas near the Duomo. Taxis are freely available but have to be hired at marked stands. Expect extra charges for luggage, night fares, or Sunday travel. Renting a car and driving yourself is not a fun experience in Milan and is best avoided. The historic area around the cathedral is good for pedestrians and a number of attractions can be reached on foot.