La Sagrada Familia - we almost didn't go inside; we thought that it'd be just as beautiful as the other several cathedrals we had visited. We finally caved in after mom's powerful tricks of guilting us, and once again, mom was right! If you're going to visit, make sure you purchase your tickets online, at least the day before, because they go out quickly. Your tickets will have a set hour at which you can enter - they do this to space out the crowd of tourists. We didn't think it was necessary to take a tour to the top of the cathedral, and I think we made the right choice. We just wandered in awe under the shimmering rainbow of lights, and it was perfect.