Barcelona

Casa Batlló – (One of the most interesting and unusual houses in Barcelona)
Food @ Boqueria Market off the Rambles
You can see my pics at my personal blog at:
http://www.gadtravel.com/2008/07/barcelona-lisbon.html

Lots of wonderful sights to visit in Barcelona, with just three days you will need to choose and plan carefully! Definitely a highlight is the Palau de la Musica Catalana (concert hall) -- you can go either for a tour (make an advance reservation, in English or another language of your choice), or for a performance, if one attracts you during your visit. I did both, and loved both! Also really enjoyed the English tour of the Hospital Sant Pau, a beautiful complex which is a 15-minute, slightly uphill, stroll from the Sagrada Familia. Especially impressive given that it was initially endowed and constructed as a hospital for Barcelona's poorest residents. I missed out on the museums and others sites on Montjuic, and also the short trip to Montserrat, but they are on my must-do list for a future visit. You mention Parc Guillermo, I've never heard if that one, do you mean Parc Guell?

I would recommend Montjuic, possibly the best lookout point in Barcelona. We took the cable car up and then walked down, stopping at Joan Miró Museum. Interesting building with some great views even if modern art is not your thing. To finish off the evening we ate at Taps Bar, then walked back to our hotel with the other Spaniards doing their nighty paseo.

Barcelona is great, probably one of my favourite places. I visited around 3 years ago now and the weather was gorgeous, it was so hot. Those spots are probably the main ones and the only ones I visited so I couldn't really suggest any different ones. I hope you have a great time!