The apartment is in an excellent location, with taking just a few minutes walk to reach Alexanderplatz and Museum Island, with the Hackescher Markt transport hub also located within a very short walking distance. There is a large Kaufland grocery store across from the apartment building for your shopping needs, with a wide variety of restaurants in the immediate area. We parked our minivan at the Parkhaus Dom Aquarée during our stay which is about 200 meters from the property, although you can live park to drop off, if necessary, in front of the building as it sits on a dead end street. This parking garage is very large and easy to navigate, with a cost of 20 Euro per day. We picked our apartment keys up at a restaurant directly across from the apartment and the process was fast and simple. The restaurant was also quite good!
The apartment is serviced by two elevators and we never really had to wait for one during our stay. The apartment itself was comfortable for our party of five (2 adults and 3 teens) and having two bathrooms was an immense benefit. We found the beds comfortable and the flow of the apartment to be great. As others have noted, the pillows are little flat and the provided towels are a little thin, but this has been the "normal" experience in our travels and we were able to bring along some of our own as we live in a different area of Germany and drove to Berlin. The kitchen is very well equipped and we found the apartment to be comfortable in every regard.
There is some intermittent train noises that will reach the apartment, but there are fans available for use, so the ability to create a bit of "white noise" helped to mitigate what reached the 21st floor. Overall, if we were to return to Berlin with a similar sized group, we would absolutely stay here again. Hae-Ok is great host and the communication that was provided was timely and helpful.
We looked at many properties in the Berlin area for our four night stay and Hae-Ok's apartment offered the best location (by far) for our needs.