To rent a car in Barcelona, you have to introduce your passport and driver license. Rental cost varies from 20 to 120 euros per day. Very often companies require a prepayment equal to the cost of the entire lease or a credit card. Actually, it`s not easy to understand the parking system as there are several categories at once, each of which is accompanied by complicated rules.
Be sure to purchase a road map and also it`s better to plan your route in advance. To tell the truth, it`s more difficult to navigate with the usual tourist map as too many streets have one-way traffic, turns to the left occur quite rarely (and even prohibited) than turns to the right. For example, Gran via de Les Corts Catalanes is formally considered a two-way street but in one direction the movement is rather trivial: you`ll have to wait until the green light comes on at each crossroad.
There are free parking spaces for travelers: near the mall-De Saint Bertrand (south-west of the Maritime Museum), near Guell Park, and near the University (but not during the session). Moving by car makes sense only if you plan to spend more time outside the city. In case you need only one-time trips (for example transfer from Barcelona airport or vice versa), it is better to use taxi.