Fantastic place in a great neighborhood — we loved our stay! Karl is amazingly responsive and helpful, and his flat is beautiful in a really wonderful old building on a terrific block. Lots of space to spread out, the flat is comfortable and sunny, and we got a kick of out staying in a traditional building. The flat is super convenient for walking to lots of sights. But also really short walks to some main metro stops, which made getting around super easy. Great shopping and restaurants nearby, and we felt comfortable strolling around at night too.
Karl really is a great host, and his flat is well appointed with a high end coffee maker, washer/dryer, and other amenities to help you feel at home. The other reviews mention the stairs, and they are what they are, but we felt the flat really added to our whole experience.