Detroit's downtown architectural corridor holds the largest collection of pre-Depression skyscrapers outside Manhattan, twenty-three buildings completed between 1925 and 1929 when the city ranked fourth in national population and architects arrived with commissions for banks, theaters, and office towers that would never be replicated at that density again. The Guardian Building rose in 1929 clad in orange brick and Pewabic tile, its lobby vaulted forty feet above a floor inlaid with Siena marble; across Griswold Street the Penobscot Building claimed the title of tallest structure outside New York and Chicago, its Art Deco spire visible from Windsor. Albert Kahn, who designed a quarter of Detroit's industrial plants, turned his systemic approach to the Fisher Building in 1928, wrapping structural steel in Minnesota granite and Belgian marble, the arcade lined with sixty retail bays and a gilded barrel vault that survived seven decades of deferred maintenance. These structures were not showpieces but working infrastructure, built to house insurance underwriters, brokerage firms, and the administrative apparatus of an industrial economy that employed three hundred thousand autoworkers within the city limits. The streetscape today reflects both preservation and adaptive reuse, with several buildings granted National Historic Landmark status in the 1980s and converted to mixed-use occupancy after decades as single-tenant offices. A Detroit architecture walking tour connects these nodes along a two-mile downtown loop, the route beginning at Campus Martius and extending west to the Fisher Building's New Center enclave or south to the riverfront where the Renaissance Center's seven glass towers anchor the skyline. Guided options offer interior access to lobbies typically secured during weekdays, including the Guardian's mosaic ceiling and the Book Tower's original banking hall. Self-guided walkers trace the same corridor using marked heritage plaques installed by the Detroit Historical Society, each building's facade legible from the sidewalk in terracotta ornament, bronze spandrels, and the vertical emphasis that defined the era's commercial aesthetic. The district's walkability improved following streetscape investments in 2010 and the return of ground-floor retail to previously vacant storefronts. Architectural historians cite Detroit's downtown as a case study in speculative construction during the final years of the 1920s boom, when developers anticipated continued population growth and the buildings were designed with expansion floors that were never occupied. The concentration of Art Deco and Beaux-Arts facades within six city blocks remains intact because post-war demolition pressure was absorbed by outer neighborhoods rather than the central business district, leaving the core frozen in a pre-Depression spatial logic. Walking tours emphasize this temporal layering, the route passing theaters converted to parking garages, bank lobbies now serving as event venues, and the original street grid that predates the automotive commute. Seasonal light shifts dramatically in the urban canyon, morning sun illuminating east-facing terracotta and late afternoon casting long shadows across Woodward Avenue's forty-foot width.