Loved it! This is a park conceived of by Eusebi Guell and designed by Antoni Gaudi with construction starting in 1900. It was to be a planned community with luxury houses which didn’t succeed. It was eventually taken over by the city and made into a public park.
There is a central part which is now a Unesco heritage site and which houses most of the things to see. This central part requires a paid ticket and you can only enter during the time on your ticket. However you can see some of it from the outside, from the free area, but this is one case where I recommend buying a ticket and going inside.
Here are pictures from inside:
If you are more into taking a quick look at mosaics there is still a lot to do in the park. There are picnic tables and benches with a great view of the city.
Here are pictures from outside:
Tickets – Access to see all the mosaic work up close costs €9 for an adult less for children. But as noted you can access the outer park area and enjoy views down onto the wall and over Barcelona city for free.
Booking tickets online is a bit cheaper but we were uncertain about the timing since the tickets are timed for entry. As it was, on a coldish, weekday in February there were only five people in line before us so it didn’t take long to get tickets.
Getting there – If you use a map program it will most likely tell you to take a subway and then walk or take a bus (for example, L3 to Vallcarca, or L3 to Lesseps and bus 24). However, we took bus 24 from Placa de Catalunya all the way. It didn’t that long and it was nice to see the city from above ground.