Just had a wonderful 4 day stay at Karsten's place in Mitte with my husband and 10 month old son. Easy to reach on public transit, though we ended up exploring the whole city on foot. Private, quiet, open, lots of light, a great place to relax after a long day out in the city. Really wonderful attention to detail, from shampoo/toothpaste/showergel/extra towels and toilet paper/blowdryer in the bathroom to a pantry stocked with tea, spices and other basics. On top of this there were lovely little details like beautiful objects in ceramic, glass, and wood, interesting books and artwork, lovely antique furniture, and plants. Karsten was incredibly flexible about checkin and checkout, brought us a cot for our baby to sleep in, and made the most wonderful suggestions for activities and restaurants, both nearby and further away from Mitte. We managed to have a wonderful trip and felt like we really experienced Berlin without opening a single guidebook. I would definitely book this place again, and recommend to anyone visiting Berlin.