If you like modern architecture to the point of being slightly geeky about it then get yourself down to Domusae - in the old Museo del Ejercito on Calle de Méndez Núñez 1 (nearish to the Prado) before 16th June 2011 when the exhibition is gone forever! It's a stunningly exhibited selection of cultural buildings (libraries, museums, public archives) from around the country. All of the projects are gorgeous and are either new or older buildings that have been rehabilitated with a modern edge. Models of the buildings and in-depth interviews with the architects are presented beautifully in the old Salon de Reinos - picture below. It made me realise that often when visiting famous Spanish cities I made a beeline straight for the old classics missing out on many modern gems. Definitely worth a couple of hours of your time.