We loved our stay at Carlos place. The location it's amazing, just in front of Mercado de San Miguel. It's a crowded area but the flat is very well insulated, so you can have a great sleep with a steady temperature all the time. The flat had everything we needed, it's also very sunny and comfortable. Carlos was super nice and willing to help all the time. We would love to be Carlos guest's again next time we visit Madrid. :)