I've had a wonderfull stay at Karsten's flat.
The flat is really central and at the same time really close to the subway if you feel lazy and don't want to walk the 10minutes to the animated quarter.
The atmosphear is really pleasant and cozy due to the perfect decoration. The whole flat is a bit atypical (central bed) but everything is so well thought that the experience is even better. I guess there is a place to sit for each mood in this flat ;)
Finally Karsten is really nice and accomodating for the hour of checking/checkout.
Great experience, will surely come back again