Human activity has ranged across the landscape leaving footprints in every corner and clime. Some of our tracks are insubstantial and easily effaced by natural forces; others are disfiguring, virtually indelible. We have trampled the earth, creating pockets of devastation, temporary and permanent – holes in the forests, holes in the mountains, and now holes in the atmosphere. But in favored locations, civilization has built rather than gouged. If deforestation, mine tailings, and ozone depletion are the negative evidence of culture's historical presence, the city is culture's positive manifestation, testimony to human creativity in the midst of so much destruction, evidence of the attempt to achieve constructive permanence among so many other transitory undertakings.