It would be hard to find a better location in Madrid! 100 metres from el Cortes Ingles, which has a food hall to rival Harrods, if you want to eat in. 5-10 minutes stroll from many of the best sights in Madrid: the Palace, Templo de debod, markets, Grand Plaza, Opera, etc. A spacious apartment, with comfortable beds and views out over the pedestrianised C. del Arenal. USB charging points by the beds and lots of other little details that are welcome.
The Museum district is about 20 minutes walk away, or can be easily reached by Metro or Taxi.
Our only quibble was that a few more kitchen utensils and some kitchen basics would be welcome. But that's a small detail - its a great place to enjoy for a visit to Madrid.