Maria accelerated without thinking -- for a few seconds, almost believing that she'd chanced upon a park of some kind, an impossibly well-kept secret in this decaying corner of the city. Then, as the illusion collapsed -- punctured by sheer implausibility as much as any visible flaw -- she pedaled on wilfully, as if hoping to blur the imperfections and contradictions out of existence. She braked just in time, mounting the narrow footpath at the end of the cul-de-sac, the front wheel of her cycle coming to a halt centimeters from the warehouse wall.

Close up, the mural was unimpressive, the brushstrokes clearly visible, the perspective obviously false. Maria backed away -- and she didn't have to retreat far to see why she'd been fooled. At a distance of twenty meters or so, the painted sky suddenly seemed to merge with the real thing; with a conscious effort, she could make the border reappear, but it was hard work keeping the slight difference in hue from being smoothed out of existence before her eyes -- as if some subsystem deep in her visual cortex had shrugged off the unlikely notion of a sky-blue wall and was actively collaborating in the deception. Further back, the grass and statues began to lose their two-dimensional, painted look -- and at the corner where she'd turned into the cul-de-sac, every element of the composition fell into place, the mural's central avenue now apparently converging toward the very same vanishing point as the interrupted road.

Having found the perfect viewing position, she stood there awhile, propping up her cycle. Sweat on the back of her neck cooled in the faint breeze, then the morning sun began to bite.