The metro is definitely the fastest way of getting around Barcelona. In summer it is air conditioned, in winter it is heated.
There are two subway systems in Barcelona, one is the Barcelona metro service, represented by coloured lines on the Barcelona metro map and the other system is the FGC subway trains. The FGC lines are indicated in blue on the map. They are faster, as they have less stops and go outside of Barcelona city.
Prices in November 2011: A single, one-way metro ticket costs 1,45€. If you are planning to use the buses or metro more than 5 times on different days buy a T10 ticket (valid for 10 trips) for 8,45€ or the T-Dia pass for unlimited travel on one day (6,20€). You can also get T50/30 tickets for 33,50€ for 50 trips in 30 days, or a T-Mes pass for unlimited transport over one month (51€). All travel pass options are valid on the bus, tram and metro.
The transport office also offers a range of tourist passes you can use on the metro, which you can enjoy an unlimited use for 2 consecutive days (11,50€), 3 consecutive days (16,50€), 4 consecutive days (21€) or 5 consecutive days (25€). These passes can be also used on the buses, FGC, Rodalies Renfe (zone 1 only) and TRAM.
Monday to Thursday, Sundays and holidays: 5am-12am
Fridays and day prior to public holidays: 5am-2am
Saturdays: non-stop service