After Seattleites carved Pioneer Square out of lush forestland alongside Elliott Bay, businesses in our city’s first neighborhood were constantly battling floods and sewage backup caused by the bay’s tides. When the Great Seattle Fire destroyed much of the area in 1889, city officials decided to solve that watery problem by raising Pioneer Square’s street level by one floor.
To allow light into the dark network of passageways of the original street level, now underground and being used primarily as storage space by businesses above, small glass prisms were embedded in the new raised sidewalks, custom designed to maximize light from above. While originally clear, the glass eventually turned purple, a reaction of manganese in the glass to sun exposure. Over the past century, many of the original skylights have been broken and removed; some have been replaced with new prisms dyed to match the aged purple. These historical remnants pepper the Pioneer Square pavement; view them from below on an underground tour, during which you walk along the original sidewalks and see what’s left of some original storefronts.