I don't know how to explain how perfect this location is. Maybe 5-10 minutes from the train station (Central), just around the block. Right around the corner from the square and Grande Place. Even though it's so very close to everything, the apartment faces a very quiet courtyard and is isolated from the noise of the square.
It's hard to describe just how quiet it is. The walls are over a foot of concrete, even interior. We never heard our neighbors except occasionally when the gate entrance opened. It was very private.
There's a community washer/dryer for 6EU per load (including drying), just across the hall.
The flat itself is a little small, but roomy enough for the 4 of us. Wife and I were on the queen in the bedroom, boys shared the queen-sized fold out sofabed. Full bathroom, modest but equippeded kitchen.
There are a bunch of small grocery express stores nearby. The big supermarket is maybe 5-7 minutes walk right down the street. And of course tons of food options right outside.
We loved our visit to Brussels and would recommend the apartment to a couple or small family. Marcelo is nearby and quick to answer questions if needed.