Citadel - White I accidentally inverted the original Citadel while fiddling in Potatoshop and quite liked the effect, so here it is only sharper and cleaner.
Quadrant I love asking people to guess the scale of this one.
The Cage I visualised the face of this one years before I managed to model it, but the shadows worked out far more interestingly than I expected.
Split Toroid (after Keizo) I only consciously realised the resemblance of this one to Keizo Ushio's granite sculptures when I was looking through a catalogue of a recent Sculpture By The Sea several weeks after modelling it...