Blue Jewel was an excellent place to stay for our time in Berlin. It is a little ways outside of the city, but conveniently located for anyone with a car, and local to numerous amenities and great, excellently priced food.
Not only were the rooms immaculate and tastefully decorated, Katharina herself was incredibly helpful and welcoming. I would wholeheartedly recommend this location to anyone staying in Berlin, and also check out Katharina's Portugal location for any trips nearby there.