shadows of the neosilk-and-nanotube filaments that hang the city from the hundreds of five-kilometer-high towers that encircle it. (A civic agent notices you noticing, and attaches itself to your infospace, whispering statistics — “Each object’s suspension must weather a class 5 hurricane and the destruction of 80% of the towers” — “Frankfurt’s current population is stable at 53 million” — “Average age 62, birth rate 0.22, net immigration of half a million a year” — “Current personal squatright: 311 cubic meters per resident” — until you brush it away.) You’re watching her lean out. The wind whips her hair, ruffles the skirt around her knees. She must be a tourist. You remember your first trip to the upper levels: leaning over the edge into the angry swarm of