Go for a swim in the sea! There is a Meet Up group for Open Water Swimming with an event almost every day. Check out the group, they are super friendly and they wait for you if you're tired :). There are even free lockers on the beach (look for the building with a red cross). The water is shark free and pretty warm from mid May on. http://www.meetup.com/Sea-swimming-in-Barcelona-all-seasons/

You may want to get inside, and it's pretty cool, but the best can be seen from the outside. This house and the ones around were designed by the best architects of the modernist period.

It's cheap, it's good, the guys are friendly and it's not too far from the beach. Their lunch menu includes a "carajillo de Baileys" (Coffee with Baileys) if you ask for it.

Ever heard the song "Horchata" by Vampire Weekend? https://www.youtube.com/watch?v=58g9PJkqW94 Horchata is what people drink in Barcelona when the weather is too hot. It is a sweet juice extracted from some kind of small potato. The first sip is kinda weird but you may end up loving it like everyone there. Add an ice cream ball in it if you're shy! You'll have the absolute best horchata at Sirvent, don't be afraid of the line, it goes fast. :)

Definitely the coolest thing you can see in Barcelona. The line is long, go early or bring a good book, because you have to see both the inside and the outside of this modernist church.

All my visitors in Barcelona wanted to have tapas. But after eating deep fried stuff for a week your body and your self esteem may collapse. If it happens, go to the Mercat de Santa Caterina for dinner, check the dishes that are being cooked on the digital screen and pick some good, healthy, catalan stuff. If you have never tried a gazpacho or a salmorejo (some kind of cold tomato soup), you should. I hated my first one but now I could drink it every day.

Ok, if you really want tapas, go to Bar Ramon. You'll have to go very early or call to make a reservation. These are probably the best tapas in Barcelona. They take their ingredients from the beautiful market that is a few meters away.

You can go to any bar in the small street called Parlament and have a great homemade vermouth. When people in Barcelona meet to drink something before lunch or before dinner, they call it "doing a vermouth". It means they drink vermouth and have something small to eat (remember they have dinner very late). Vermouth is similar to red Martini. Some of my visitors didn't like it at all though... :)

Good concerts and the best disco for electronic and rock music. https://www.sala-apolo.com/en/