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.
The Tomb of Porsena is a legendary monument built to house the body of an Etruscan king. 400 years after its construction, the Roman scholar Varro gave a detailed description of the ancient structure. A giant stone base rose 50 feet high, beneath it lay an "inextricable labyrinth", and atop it sat five pyramids. Above this was a brass sphere, four more pyramids, a platform and then a final five pyramids. The image painted by Varro, one of shapes stacked upon shapes, seems like a wild exaggeration. Despite this, Varro's fanciful description sparked the imaginations of countless architects over the centuries. The tomb was an enigma, and yet the difficulty in conceptualising it, and the vision behind it, was fascinating. On paper artists were free to realise its potential. If paper liberated minds, the screen can surely open up further possibilities. There's no shortage of visionary structures within the virtual spaces of video games. These are strange buildings that ask us to imagine worlds radically different to our own.
Whilst many impossible formulations are orientated towards the future, there are also plenty from the past. The castle in Ico is one example of this. During the Renaissance, Europe was obsessed, not with future utopias, but with ancient Greece and Rome. While the box art of Ico is famously inspired by Giorgio de Chirico, the long shadows and sun-bleached stone walls only make-up a portion of the game's mood. It is the etchings of Giovanni Piranesi that best capture what it's like to explore the castle's winding stairs and bridges. Piranesi's imaginary Roman reconstructions were absurdly big - so colossal you could get lost in just the foundations. In a similar way, Ico's castle is impossibly large, the camera zooming out in order to overwhelm you and build up the unfathomable mystery of its origin and purpose.