Contaminated drinking water killed thousands of Chicago's original citizens, so the city took the unprecedented step of digging a tunnel two miles long and 30 feet below lake bottom. Since the facilities on shore included an unsightly 138-foot vertical pipe, famed architect William Boyington concealed it with a limestone, castle-like tower that soon became a celebrated landmark. Through the first 150 years of its existence, Chicago's iconic Water Tower has survived the Great Fire-the only public structure in the burn zone to do so-and at least four attempts at demolition. John Hogan pays tribute to the beloved monument that accompanied the evolution of Michigan Avenue from cowpath to Magnificent Mile.