The ticket for all means of transportation costs €1,40 and usable for 90 minutes after its validation. There is a cheaper ticket at €1,20 but that's valid for just one ride on all means of transportation except the metro.
24h tickets cost €4 and 7day tickets cost €14.
There are also monthly and yearly unlimited travel cards at various costs. For info call 185 or ask at any public transport ticket kiosk or metro station. Fines for fare-dodgers are 60 times the price of the ticket.