There are several transportation options for getting from Barcelona airport to the city. The most convenient and cost-effective way is by taking the Aerobus, which runs every 5 to 10 minutes and takes around 35 minutes to reach the city center. Another option is to take the RENFE train, which is faster than the Aerobus but requires a transfer to the metro to reach the city center. Taxis are also available, but they can be more expensive.