A smaller number of unbuilt projects haunt architectural discourse as provocations. They are like ghosts that never fully leave the conversation – fading from view sometimes only to be rediscovered by another generation of architects, and rediscovered with greater passion than before, even becoming ever more urgent. These ideas of possible future constructions uncannily capture the imagination of architects that are engaging very different times, places, scales, concepts, strategies, and technologies. The projects permanently hover on the threshold of being realized or force the field to keep thinking about what it would mean to realize them. They are question marks. In fact, they are designed from the beginning as question marks... [+]