the Airbnb is located a few minutes walk from metro stations, easy to find, clean, a bit small but fine for a few days for a couple.
HOWEVER, do notice that communication with the host is close to nonexistent. it takes a few hours until the host responds.
also, there is no place to leave your luggage before check-in or after checkout so in this case you either walk around the city with your luggage or pay extra for a locker room near atocha station.
the host did try to check us in early (at 13h instead of 14h) but since we arrived early we had to walk around with our luggage for a few hours.