I can't recommend Samtiago's apartment highly enough - I'm not surprised it's so popular (we were lucky to get it at such short notice). The Green House is close to the metro, easy to find, clean and stylishly decorated with the most wonderful terrace - we'd have happily stayed forever! It's astonishingly close to the Reina Sofia, the Prado and Museo Thyssen and much else besides. If you're looking for a home while you're in Madrid, you can't do better than the Green House!