This is a beautiful dinky little apartment with pretty much everything you need to explore Madrid. WiFi and Aircon worked well, location is brilliant next to Atocha station and next door to all the major museums, the Retiro and Botanics. Not a lot of space/storage but there is enough to base yourself out of to explore around.
Guys at Redkey were very friendly and helpful but we experienced some communication delays which was frustrating. Overall however it is a lovely apartment and gets our recommendation