Barcelona is a reasonably huge metropolis. You'll be able to walk to a lot of the principal attractions. But, when you’re in Barcelona for 3 times, you’ll finally find yourself looking for transport. Take the metro or taxis. Skyscanner gives a ‘Greener flights’ filter highlighting flights that emit a lot https://www.triptales.me/unlock-barcelonas-hidden-treasures-secret-spots-you-cant-miss/