Philadelphia1, once the second-largest city in the British Empire, is still a major American metropolis, with its 1.4 million city-dwellers and almost six million suburbanites living in the surrounding hills and valleys. Every day people venture in their hundreds of thousands over congested roads, or by rail and trolley2, to the three-centuries-old 'City of Brotherly Love', where 18th-Century brick built by Quaker foresight stands cheek-by-jowl with modern towers of glass and steel.
