I recommend Henrik's apartment for a single person or couple visiting Berlin! The listing was very accurate, and the apartment itself is cute and has what you need for a weekend. Good heating, nice shower pressure, and a remarkably comfortable bed! Check in was a breeze, and Henrik himself is great to communicate with.
It is in a great location, near public transportation and many lovely cafes and eateries. It was easy to arrive from the main train station, and we walked easily to landmarks like Alexanderplatz and Museum Island.