Sounds like a fun trip..
Barcelona is a 'must see'...
I'm sure Paco can give you more details.. but a few top sights..
Picasso Museum in the Gothic Quarter..
Mies van der Rohe's 1929 Barcelona Pavilion...re-constructed in 1986.. one of the seminal buildings of all time...
Gaudi's Parc Guell, Casa Batillo and cathedral..you might also see if you can find the 'Dragon Gate'...a fantastic wrought iron and cast iron gate to one of the properties near the Parc Guell,
Also if you head out a little to the west go to the top of Torre del Collserolla, great views.. its also a great building....
