I stayed in the apartment for 3 days and it was perfect as it is very centric, lots of shops around and a train station very close. The apartment is in an old classic building from Madrid, tiny but ideal if you just want a place to sleep and have a shower because you'll be out all day. The kitchen is little but with all the basics to make your breakfast or quick coffees (Nespresso included!). The only thing keep in mind you need internet to have access to the building for first time so if you're coming from overseas buy a sim card with internet (I bought one at a shop on the same block, very helpful).
The building has a lift and the main door is very safe.
Highly Recommended!