If you found Madrid boring then you must be a very boring person. Not to be missed - the 3 great art galleries including the Prado which are all very close to each other - among the best in the world.
Madrid is a beautiful city - not at all boring. Take the open top bus tours around the city. If you like football go see the Bearnabau - they do tours. Lots of beautful buildings, lots of great resturants too. You'll have a great time - wish I was going again.
don't know how much time you have, but just let yourself wander through the streets, find squares, tapas bars(especially in the eve.!) parks, watch the crazy Madrileno's and join in!!