Barcelona is one of my favorite towns. While I am not a foodie by any stretch of the imagination, even I found the food to be amazing.
If you are a Gaudi fan then Barcelona is the place to see. Some of my favorite places are Casa Vicens, Casa Mila (La Pedrera, and one of the most recognized the La Sagrada Familia Church. Want to spend the afternoon outdoors then a visit to Parc Guell is a must.
Soccer fan? Take a tour of the FC Barcelona stadium or better yet attend a game. If you are a soccer fan from the US and have never been to an international match - then you haven seen soccer! Nothing compares to this experience.