The city has been excavating and hewing cuts through the land since its beginning, but what many Seattleites don't know about is the pedestrian tunnels and other covered connections downtown. Here's the inside scoop.

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It’s easy to walk by the small set of stairs near the entrance to the 5th Avenue Theatre in downtown Seattle and never notice it’s an opening to a tiny under-cover world, one with shops, restaurants, artwork, old photographs and a hidden passage to nearby buildings.

It’s not exactly a supersecret thoroughfare, but there are still plenty of local folks who’ve never heard of it.

Take Leslie Davidson: She was born and raised in the Emerald City, where 155 days of rain a year and temperatures above 73 degrees send people scurrying for shelter or shade. Yet she knew nothing of Seattle’s subterranean walkways until a friend took her children on an expedition of the Pedestrian Underground Concourse that cuts under four city blocks.

“They still talk about it,” she said of the decade-old adventure. “They got to go all the way down underneath the city and they never got wet though it was pouring.”

Her friend Eric Makus was introduced as a child to the underground concourse, which — until the  current redevelopment of the Rainier Square skyscraper  — provided an unbroken passage from the theater to the Washington State Convention Center. In the years since, he’s made it his mission to seek out and traverse every concealed corridor and sneaky shortcut in Seattle.

“One of the fascinating things about these passages is that once you know about them, it seems obvious you’d use them as a shortcut and a way to get out of the rain,” said Makus, an attorney and urban explorer. “But you usually have to have someone show them to you.”

‘Powerhouse of tunneling’

The city’s most popular under-cover passages and pedestrian tunnels are just a tiny portion of Seattle’s under-cover infrastructure that includes more than 150 tunnels and covers 74 miles, built primarily for sewers, utility lines, land stabilization, railroads and transit.

The city has been regrading, excavating and hewing cuts through the land since its beginning, defining Seattle as “the biggest powerhouse of tunneling on the West Coast,” according to Robert “Red” Robinson, the director of underground services for Shannon & Wilson, a geotechnical and environmental consulting firm here.

In a scholarly paper updated most recently in 2013, Robinson outlined the city’s 130-year-old history of digging through the region’s challenging terrain, from glacially sculpted ridges to shifting layers of sand, gravel, clay, hardpan and all kinds of boulders and rocks.

The city’s first tunnel, the Lake Union Sewer Tunnel, was dug out of fear. Workers excavated it by hand in the late 19th century, following a cholera outbreak in San Francisco. City planners had realized it was not a good idea “to pour sewage into Lake Washington where they got their drinking water,” Robinson said.

Over the next three decades, the city had excavated the Montlake Cut to connect Lake Union and Lake Washington, dredged the Lake Washington Ship Canal and moved 50 million cubic yards of soil in a series of regrades that leveled ridges as high as 200 feet, including Denny Hill and the land where Seattle Center now sits, which was once a 100-foot peak.

The city also laid down the double-track, miles-long Great Northern Railroad tunnel that runs beneath the city center. That railway was completed in 1904 by 350 workers with pickaxes, shovels and wheelbarrows. It was, at the time, the highest and widest tunnel in the U.S.

“The city seemed to have no trouble getting things done in those days,” said Robinson.

Since then, the city has racked up a number of other notable engineering feats:

• The triple-deck, five-lane Mount Baker Ridge Tunnel for Interstate 90 was completed in 1986, despite occasional encounters with boulders as big as 10 feet across. The roadway, with an inside diameter of 65 feet, remains the world’s widest built in soil.

• The Downtown Seattle Transit Tunnel runs beneath Third Avenue and Pine Street, connecting the International District to the convention center. It was the first tunnel built for both buses and rail lines. It was also the first tunnel coated with a waterproof PVC lining and unreinforced concrete, according to Robinson.

• And now, Seattle can boast that its most recent transit channel, the Highway 99 tunnel built to replace an aging and earthquake-shaken viaduct, was drilled with what was then the world’s largest diameter boring machine. That drill, named Bertha, boasted a cutterhead diameter of 57.3 feet.

Hills and rain

Why did the city become such a mecca for tunnels, both large and small?

Robinson, who said he’s had the good fortune to work on most of Seattle’s tunnels since the ’80s, said during a recent walk through the Pedestrian Underground Concourse that he thinks it’s a mixture of common sense and mercy.

“It’s because it’s so hilly and so rainy,” he said. “One of the reasons, I think, that we have so many pedestrian tunnels is because the people who built them did it out of pity for the pedestrians.”

Using the tunnels and shortcuts are the smart move, said Makus; “We all want to save time, we all want a more direct route and we all want to avoid hills.”

For those who want to explore for themselves, here are six pedestrian passages, in addition to the 5th Avenue concourse, that are located in the core of Seattle.

• The Justice Center Tunnels connect the King County Courthouse to the county administration building, a parking lot and the county jail. The passage from Fifth Avenue to the King County Parking Garage features artwork by Michael Spafford and by Bill Fitzgibbons. It’s often used by veterans of the court to bypass the long lines that can form at the courthouse’s Third Avenue entrance.

• The Columbia Center Pedestrian Tunnel, built in 1985, connects the state’s tallest building with the Seattle Municipal Tower and 800 Fifth Avenue. From here, you might find the highest concentration of people in business attire in the city and access the top of Columbia Tower to see a sweeping view from Mount Rainier to Mount Baker (check the weather forecast).

• The Pacific Place Passage begins inside the Barnes and Noble on Seventh Avenue and Pine Street, winds through Pacific Place, Nordstrom, a skybridge and the Westlake Transit Tunnel before ending at Macy’s.

• The so-called Benaroya skip is a little shortcut that uses the University Street Transit Station to bypass the hill between Second and Third avenues.

• The Northwest Kidney Center Tunnel connects the kidney center to Swedish Medical Center and the 600 Broadway Building. It crosses Broadway, takes you to the hospital’s cafeteria and sits right on the edge of Seattle University.

• And, of course, there’s the under-cover Pike Place Market, which spans from Victor Steinbrueck Park at Western Avenue and Virginia Street to First Avenue and Pike Street. In the early morning, vendors are setting up their stalls, filling them with local wares. During the busy tourist season, the passageway might not be a quick jaunt, but “it’s about as Northwest as you’re going to get,” Makus said.

Though it’s not a thoroughfare, there’s also the Underground Tour of the streets and shops entombed when Seattle rebuilt itself after the Great Fire of 1889.

A jaunt through one of these passageways can be a small reminder that Seattle has a history of reshaping as it goes and bending the landscape to its will.

“It’s convenience and expediency combined in little hidden gems,” Makus said.