Flat has 3 bedrooms and three bathrooms, which is fine for big groups. The flat has modern look, but it's a little bit used. (sofa, bathrooms and walls). The hot water goes max 10 minutes ( 2 people do shower) and then you need to wait 30 - 50 minutes to get hot water again. I think the boiler had some issue, so it should be repaired for your stay. The location of the flat is in Embajadores / Lavapies area. The street itself is not the nicest street in Madrid, but surely safe. It' s about 15 minutes walk to Sol and 20 minutes to the Palacio de Real. I missed in the kitchen some basic amenities like kettle to make a tea, kitchen towels / salt, sugar.
The communication was great and the check- in was also smooth.
Last thing, it's hosted by a company. I booked stay with Tarek, then I communicate with Maria and checked in with Cande.