Parc Guell was originally designed by Gaudi to be a small area of residence in Barcelona. The project never succeeded, though, and the city made it into a park some years ago.
From the bottom side of Parc Guell, there are two options to get up. One is the easy, relatively painless escalator. Unfortunately, on the day we visited, the escalator was not functioning. The second way is to climb several hundred stairs, which is far more painful, but we had no choice.
The park is easily worth the climb. There are fantastic views of the city, amazing sculptures within, and a lot of shade. The scupltures are awash in color, and many of them are lizards.
The neatest thing about the park is easily the cave area. There are columns carved into the natural stone, and you can walk into the caves. From there, you get the best view of Barcelona and a ton of shade. I never knew there were cactuses in Barcelona until I sat in the caves!
Admission is free, but there is always the overpriced concession stand.