Although this is not to be missed on a visit to Barcelona, I have to say that it was a slight disappointment, especially after the visit to 'La Pedrera'. I think this, however, may largely be due to tourist hype rather than anything else!
The outside is very impressive from both sides, but once inside it is much more of a building site than one would perhaps expect when the timescale of building has been taken into account, and unfortunately this means that once inside there is very little to do other than either climbing up the towers or getting the lift (for which the queues can be unbearable). The views are far stretching and on a clear and sunny day very pleasant although you can get much the same from the top of 'La Pedrera'.