It's worth huffing and puffing the 459 stone steps to the summit of La Gran Piedra at 1234m. The huge rock on top measures 51m long and 25m high and weighs... a lot. Its popularity and commercialization goes a little unchecked (cue the eager trinket salespeople on top).
On a clear day, there are excellent views out across the Caribbean, and on a dark night you can see the glow of lights from Jamaica.