The appartment itself was great, as the location too! I absolutly don't wanna make it seem bad, but I think some things are important to know.
First of all the walls are really thiny, that means you can hear nearly everything- fortunately after writing to Daniel, he reminded the other guests that after 22 p.m. there should be silence and it was.
Second, the couch-bed mattress isn't flat, there is like a hole in the middle.
Last critic: in the stairwell it smells terrible like a dirty cat's litter box.
For the rest it's really cool! you have everything you need in the appartment, it's clean, the shower is great, you're in the center of Madrid- you don't need to take metro or busses, you can walk to every importante place.
I really enjoyed those days with my family in the appartment and will chose it again for my next trip to Madrid!