This is something I came across, and even though I've seen a fair few of them around, this one really has been done very well, and the resolution of the images is breathtaking.
The clever people at VRWAY Communication have created some amazing virtual tours in 4 dimensions for various cities, Barcelona being one of them. This serves various purposes in my opinion including planning a trip and what to see, to simply seeing the sights you already know if you live here/have been here before - but on a gloriously sunny day!
Imagine the situation, you've only got 3 days in Barcelona and have been scouring the web for information on what to see and what not to see - some people say you must visit one thing and you're not sure if to go for it or not. Problem soved! Go to the website here and have a good look around!
I've included a few screenshots here of what some of the images look like, but you really have to have a look at the site yourself, and have a little play around - it's great fun!! If you're looking for some accomodation for your stay in Barcelona, why not opt for an alternative to the usual hotel room, and go for a self-catering apartment for rent in Barcelona ? There are some great deals to be had, and it gives you much more freedom to explore the city and it's sights, too.