Below the streets and sidewalks of Pioneer Square, you can get a glimpse of Seattle as it was in the late 1800s.
"The old street level used to be one level down from what it is now," explains Lorelei Williams, with Seattle Department of Transportation (SDOT). In 1889, a fire ripped through 25 city blocks .
When the community rebuilt, they built up - literally.
"We had the building fronts on one side, and then we built up the streets on the other side...and then we basically put a cap over the top of it, and that's the sidewalk." Williams says.
The streets around Pioneer Square aren't built over air spaces. The city filled the space under the streets with dirt and pipes for water and sewer. But there's a comparatively weak spot right by the curb, where the street is held up by that underground wall.
The walls are more than a century old, and they were built to handle horses and carriages - not delivery trucks that weigh thousands of pounds. When the Alaskan Way Viaduct closure forced buses onto First Avenue, city crews looking for new bus stop locations realized that the strain of traffic was beginning to show up underground.
Experts say Pioneer Square is safe. But in order to keep it that way, the city needs to take immediate action.
This weekend, signs will go up banning delivery trucks from driving or parking in the lanes closest to the curb. It's an effort to ease strain on Pioneer Squares' underpinnings while crews work on figuring out which walls are safe, and which ones need reinforcement.
"The loads on the street transfer through the soil to this wall," Williams explains. "So by moving that load further away from the wall, there's less pressure on the wall itself."
While the restrictions are sure to inconvenience anyone trying to run a business in Pioneer Square, visitors will not be impacted.
"The load restriction is only for vehicles 10,000 lbs and over," says Alliance for Pioneer Square Executive Director Lisa Howard. "So it doesn't affect your car, or even a large SUV. Individuals can still come down; get through the neighborhood; park and shop safely, and have nothing to worry about."
Howard says SDOT has been working closely with business owners to make sure they get the support they need while crews are working on ways to support the streets.