I have been to that place!!!! It is in Rotterdam, the Netherlands.... or was it the Hague? Anyway, twists your mind to walk around in there...
One way to save on digging foundations, as long as the boulder on the left did not decide to roll down the hill.
Those full height glazed doors on the upper floor allowed more light into rooms enclosed by a pitched roof, they also served as a fire escape.
Full height doors are often used on roof extensions in London, for both the reasons I mentioned. Roof extensions are often only allowed on the rear elevation of houses, so fire rescue can take time.