You could just leverage all those iPhones, iTouches and the coming storm of Andriod phones... Build all your content on a mobile-phone delivery system. That kind of software-based solution is really much more scalable than you're talking about. I don't know if there are systems like that in Spain yet (maybe Layar?) but you can build that content on SCVNGRs platform right now: http://www.scvngr.com/museums/

The release dates are on the teaser/poster images. Click any of 'em, or check out the one Frankie edited at the bottom of the page.