The apartment is in a fantastic part of Madrid. We were very central and only a short walk away from many places we wanted to see. Apartment was clean and well kept. Double check the fine print before booking as we did not initially see the late check in fee and all the other possible fees - that was our bad.
The only negative is that to get to the apartment unit you have to walk through the building which has active construction. There are building materials everywhere. The construction workers were wearing hard hats and started work very early in the morning. It did not feel very safe to be walking through and if you like to sleep in, you'll have a hard time. At one point the construction work was right outside the window and they could see inside which was a bit of a shock. Keep the blinds closed...