When I visited Barcelona (about 10 years ago) I didn't want to bother with a tourist trap church, but my wife insisted we go. I could not have been more wrong. The arches and buttresses inside are amazing, the facades are intricate and fascinating, and the light coming through the stained glass was nigh-psychedelic.

Barcelona is an amazing city and it's very easy to fill up a vacation with other activities - but I highly recommend spending at least half a day at La Sagrada Familia