We loved staying in Elsa's apartment!! The location is great and only a short walking distance from La Plaza Mayor and other touristy areas. It is also close to a metro station if you'd like to see the rest of Madrid.
The apartment was perfect for the three of us and we liked that there were many things available to us such as an iron and towels and even some croissants! The only problem we had was that the air conditioning machine was leaking some water but we just put a towel underneath and problem solved!
Also, Elsa is among the best hosts we have ever had. She was very accessible through messaging and full of recommendations. We only wish we could have met her in person!
If in Madrid again, this would definitely be the place to stay for us again.