Though we can't share Goldin's enthusiasm for a ""super modem. . . city in the sky. . . filled with people hustling and bustling,"" we can recognize a built-in interest in how employees of the Twenty-First-Century Development Company buy and survey a site, write the specs, obtain bids and permits, and -- after a year's paper work -- bulldoze the area, build underground retaining walls and sink footings, add grillage and columns and core, steel wall sections and floor units, and finally hold the ""magnificent"" topping off party on the roof over the 80th floor. Goldin takes the mildly curious on a quick, undemanding tour, appending a balsa wood experiment (demonstrating how -- but not why -- the shapes of I beams and H columns make steel stronger) for the more engineering minded and a glossary of 31 words, from architect and backhoe to truss and web, for those who might have missed the explanations in the text.