There is a saying in architecture that no building is unbuildable, only unbuilt. Structures may be impossible in the here and now, but have the potential to exist given enough time or technological development: a futuristic cityscape, a spacefaring megastructure, the ruins of an alien civilisation. However, there are also buildings that defy the physical laws of space. It is not an issue that they could not exist, but that they should not. Their forms bend and warp in unthinkable ways; dream-like structures that push spatial logic to its breaking point.
Years ago, I interviewed a level designer who had originally trained as an architect, which these days is not an uncommon career trajectory. I asked him about the benefits his skillset brought to 3D level design. He talked about how it helped with approaching scale and structural integrity and creating a rational space.