Harmonizing In every area of human effort, creativity is intimately associated with the quest for beauty. This is most obvious in the fine arts, but it is no less true in the practical arts like architecture and engineering. Here, especially, there is an aesthetic quality that often lies in harmony, in fitting the products of human ingenuity agreeably into their environment. Bridges are among the largest and most imposing engineered structures. In the past great bridges were built to call attention to themselves and to the engineers' ability to overcome enormous obstacles. As a result, bridges can reshape their environments: Who can today think of the magnificent natural opening of San Francisco Bay, dubbed "the Golden Gate" by early explorers, without thinking of the great bridge set across it in the 1930s? Sometimes, however, it seems best that a structure should not so much reshape our perceptions of a space as enhance them. In Colorado's Glenwood Canyon, a key link in the nation's interstate highway system required the construction of a viaduct to carry the road over a narrow, curving, and beautiful stretch of the Colorado River. The Hanging Lake Viaduct fits aesthetically and satisfyingly into this precious natural setting while providing an efficient and reliable transportation link. Meeting the challenge in Glenwood Canyon involved not only designing a structure that would harmonize with its environment but also minimize harm to the river and its surroundings. The builders used a giant gantry and crane to set the pre-cast concrete box girders into place from above. The number of piers supporting the road was reduced by