Hello!
All the sights in Barcelona are located close to each other and you can reach them by subway or tramway. First thing you absolutely must see is Gaudi buildings. La Sagrada Familia, Casa Battló, Parc Güell and many other buildings all over the city are made by a brilliant architect Antonio Gaudi. I don't know other cities in the world which would be built almost entirely by one architect (maybe in the comments you will shed the light for me?)
I wish we went to the Tibidabo mountain for Amusement Park, but it was far far away from us and we didn't have enough time for it. Though one ticket for adult is 30 EUR worth and you can visit as many rollercoasters as you want all day without any limits! That's amazing if you compare it to Disneyland.
Nevertheless, we did have a chance to take a trip on a cable car (16.5 EUR for one round trip) and enjoyed the beautiful view of the city from the mountain. A hint: if you don't want to wait in a long line, you can buy tickets on the mountain near the Miramar hotel. The station which is closer to the beach is packed with people.
Do you want to talk about night in Barcelona? Everyone knows about the Magic Fountain. It seemed to me that it was the most touristic and the most crowded place in Barcelona! You might want to come at 8 or even at 7 p.m. to enjoy the fountain seated! It was unexpected that they played even modern songs :)
If you want a less crowded place but with some sparkle, you must visit Torre Abgar! Just take a seat on the grass and enjoy red and blue colors. We entered the hotel near the Tower and got to the 10th floor, there is a restaurant over there with the view of Abgar.
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