Travel Barcelona, you will regret if you just know by without really spend time over here. It is really universal master piece of artwork, architecture or whatever you name it. Both inside and outside all kind of miracle built on the building.
I think the most important part I want to explain is that is is "different", and no so common kind of Basilica or Church in term of design. But once you get used to it and understanding the background information on it, you will love it. Master piece. Do not want to talk too much, distort your experience, try to be there and spend some time on it.