Catharina's place was great for our family of 3. It is a 10 minute walk from the Osterport train station and a few minutes walk from the bus stop. There is a pizza place and a bakery within sight, and if you walk towards the bus stop there are more restaurants and shops. It is within walking distance of the main sights, as everything is within about 1.5 miles, but we opted for the bus.
The apartment itself has a main room with a table and chairs, a twin bed and a queen bed and has high ceilings and is very bright and clean. There is a small kitchen with the basics too.
The area is very safe feeling, and away from a lot of tourists. I recommend ear plugs since it's on the ground floor and there are neighbors above.
I recommend staying here, it was great and Catharina was very easy to communicate with and gave us excellent recommendations on things to do and how to get around.