This is a pretty easy place to find if you are coming from Atocha. It's located among most of the tourist places I wanted to visit and perfect for my time in Madrid. I would recommend it for solo travelers or small groups.
The flat itself is located on the second floor without an elevator so be wary about that. I also checked in pretty early because of my train and he was very accommodating, giving me keys and letting me put my stuff down first. The place itself is pretty big and perfect for one to four people, max. The bathroom was clean and had all the things you needed. The shower does have a step but it isn't too out of the way. I would say it's a good sized bathroom for one person to be inside.
The kitchen was also clean and he had more appliances than what I expected. There was a microwave and toaster, lots of plates and cups, a fridge and stove. There was also lots of items in the pantry if you wanted to make food without having to go out and buy them. The flat is also half a street away from two convenience stores if you ever needed anything.
The master bedroom was pretty big; there is a queen sized bed in the middle of the room with large closets on the side as well as a desk and lamp. There is really good lighting in this flat and is perfect if traveling with one or two people. There was a side room with a bunk bed if you were traveling with more people. The bed was really nice because it didn't hurt my back after one night. It was also warm enough at night without me having to turn on the heaters.
The living room is a sofa with a table and tv. It's a good place to relax after coming back and the whole layout of the flat was well done. There's a lot of glass walls which was interesting. It's a bit bigger than expected from the pictures which is nice.
I would definitely recommend this place because the streets are easy to navigate and the neighborhood is a good place to be in. It isn't loud and everything that you would need is close by.