In Barcelona, the place of interest is an unfinished Church called The Sagrada Familia - one of the most renown architectural structures in the world, which was designed by the famous architect Antonio Gaudi. You have to see it yourself to marvel at the uniqueness of it. I just stood in awe and marvelled how this kind of structure could have existed. No pictures can convey the kind of feelings you get on sight. Must go there to see it yourself. The Duomo in Milan is another Church of outstanding architecture, but no comparison to this unfinished Church in Barcelona. Duomo is beautiful but you are not overwhelmed by it. You simply consider it as another church. Just seeing this unfinished Church in Barcelona is already a worthwhile trip there. Cheers