As a Barcelona local, I obviously have been to several museums and churches in the city, but I had never been to Santa Maria del Pi before today. I found it in one of those ’10 alternative things to do in Barcelona’, so I decided to do some research.
If you want to see breath-taking views, I recommend visiting this Basilica. The entrance to the church is 4€ (or 3€ if you are a student), but if you want to get to the top, you must take the guided tour that they offer daily.
Now, the price is 8.5€ per person, they usually are at 12pm and 1pm, and they are 45 minutes long. I truly think the money you spend is worth it, at least it was for me; you get a 360º view (one of the best in my opinion, alongside 'Bunkers del Carmel' and 'Tibidabo'), plus an explanation that allows you to understand why that church is there.
You can buy your tickets here (it is where I bought mine): https://www.riostabarcelona.com/en/espai/santa-maria-pi/