The client asked the architect for a one-room extension, which is what the zoning laws would permit. Since The house had only a small garden in front, facing morning sun, so the architect proposed to put the extension largely below ground, and allow for a big rooftop terrace facing evening sun and sunset. This would also allow for a more secluded location of the extended room, which was a wish by the client.
The drawback of this is that the extended room would have only views towards one direction, and risk feeling like a bunker. To avoid this, the room was split in two levels, with higher ceiling in one part, and lower ceiling in one part. This makes the main living room the center of the extension, while smaller spaces around it add depth to the space. Walls between these spaces are half translucent glass bricks, and half sliding doors. This allows for a permeable border between these two spaces, and an in-between zone where one can sit in the stairs and be in both rooms at one time.