Seattle Underground

The Seattle Underground is a set of buried storefronts, passages and sidewalks beneath the Pioneer Square Historic District in Seattle, Washington, reached today on guided tours that begin at 614 1st Ave. Its origin lies in the original site of the city, built on tidal flats that flooded at high tide, with toilets that backed up when water rose. After the Great Seattle Fire of June 6, 1889, the city rebuilt on the same spot but decided to raise the streets, in places by about 12 feet or more. Walled retaining corridors were poured along the streets, and for a time pedestrians climbed ladders between the new street level and the old sidewalks while building owners finished their upper floors. When the new sidewalks were laid over the corridors, many were roofed with small squares of violet-tinted glass, called vault lights, that can still be seen in Pioneer Square pavements. The former ground floors became dim basement spaces, used for storage and sometimes for less respectable trades, until the city condemned most of them in 1907 amid fears of bubonic plague. The guided tour, first run in 1965 after the Seattle journalist Bill Speidel campaigned for the area to be saved, lasts about 75 minutes and combines humor with documented history. Guides explain the fire, the regrade, early sanitation, the career of the pioneer Henry Yesler and the saloon and brothel culture of the old Skid Road. The route passes through rooms with original brick, ironwork, collapsed walls, abandoned fixtures and glimpses of vault lights from below. The experience is immersive rather than museum-like, with little signage and few conserved objects, because the spaces are preserved largely as they were found, with only safety work and lighting added. The passages are uneven, partly dusty and in places low, and the tour includes stairs. The tour is a good introduction to the city's frontier past, and it fits comfortably into a visit to Pioneer Square alongside the nearby Klondike Gold Rush museum.