Hostal Anton Martin is in a very good location, plenty of places nearby for meals, tapas, breakfast, coffee. Our room was at the back, so nice and quiet and little noise from other guests. Good to have air con, which wasn't too noisy and great to have a fridge. Room felt a little cramped but plenty of storage space and a decent shower in the ensuite.
Very good location for Prado,Retiro and Rein Sofia and also Atocha station. Also walkable for Plaza Mayor and Metro nearby.