Our tour began at the Monadnock Building, a somber, chocolate-colored structure near the south end of the Loop. (The Loop is synonymous with "Chicago's downtown business district," which is traditionally defined by the elevated train that runs in an oval around it.) Architecture buffs such as Samuelson and Achilles love this building because it's an anomaly, looking both forward and back. By the time it was built, in 1891, steel-frame construction was already being used to achieve height without the chunkiness of the early tall buildings made out of stone and brick. But the firm of Burnham & Root, which designed the north section, made this 16-story skyscraper the old-fashioned way--out of masonry. This meant it needed a massive base; the exterior walls at ground level are 6 feet thick. But the Monadnock was also path breaking. Tired of being nickeled-and-dimed by its Boston developers, the architects proposed an unheard-of cost cutting measure: no exterior ornament. On the north section, seen here, there's not even a pediment, just a curved lip. This gives the moody hulk a sculptural shape and a sort of Egyptoid cast, which is appropriate when you consider that the principle of its construction is that of a pyramid.