When completed in October, The Block complex on Broad Street will support up to 87 climbers at once.

The Block climbing complex, which is expected to be complete in October at the site of the former Bijou Theater, will have about 28,000 square feet of climbing space, organizers say.

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There's a man wedged in a spiderweb of steel beams that are cobbled together like an upside-down Eiffel Tower. A flash from his handheld welding torch casts a tangled shadow on the wall of the shuttered Bijou theater, which a nonprofit group is transforming into one of the largest climbing wall complexes in the United States -- and the largest in any U.S. city's downtown.

"Currently in the U.S., there is nothing of this scale," said architect Craig Peavy, a partner at River Street Architecture.

Workers will cover the mazes of welded steel with hundreds of precisely cut wood panels, each of which is pre-drilled to support climbing handholds. The Broad Street attraction, which backers call The Block, will feature 28,000 square feet of climbing wall space spread over 261 routes when complete.

"We knew whatever we put in here, we needed a lot of it," said Kim White, president and CEO of developer River City Co., which is leasing out the space.

Indeed, the former theater is a big building. Adjacent to the 23,000-square-foot climbing complex, outdoor retailer Rock/Creek is opening a 4,000-square foot store on Broad Street, which will sit next to a 1,600-square-foot coffee shop. Another 3,000 square feet is available on the Chestnut Street side, and the Chattanooga Visitors' Center will be tucked into the bus tunnel.

But the biggest draw isn't what's on the inside. It's the building's exterior that will set jaws wagging throughout the country, White said.

In this case, tourists on Broad Street will be able to look across the Tennessee Aquarium's plaza and watch climbers scramble up 14 climbing lanes spread

across the exterior face of The Block. Constructed of translucent plastic panels that each can withstand thousands of pounds of pressure as well as earthly elements like wind and the sun, the geometric skin of the facility will serve both as an architectural statement and a challenge to would-be climbers.

"Look at that, look at that," Peavy said, pulling out his cameraphone to take a photo of the new elevated platform that juts out over the sidewalk.

Visitors will walk out to the platform from the building's interior, before scaling the sides of The Block.

Lights behind the 55-foot high climbing panels will brighten the night, and two specially designed speed climbing lanes will allow Chattanooga to host international climbing competitions, as well as offer practice opportunities to climbers who don't mind an audience.

"The panels are supposed to withstand 700 pounds, but we stopped the test at 4,000 because we were afraid it would break the testing machine," Peavy said.

The $6.5 million indoor/outdoor climbing and retail complex will open on Oct. 13, backers say. White is brimming with confidence -- so much so, in fact, that she's agreed to host the closing ceremonies of the city's RiverRocks festival on that day.

By the time of RiverRocks, River City Co. and its partner, High Point Climbing and Fitness, will have added 20 jobs to the U-shaped complex, which will retain the parking garage on its upper floors. The formerly vacant interior space will include a bouldering area as well, which will challenge climbers to scale a boulder-type obstacle without the aid of ropes.

"There will be numerous bouldering walls that will include a wave wall, mushroom, arch, moon wall, campus wall, adjustable wall, and a 70-foot long cave in the main bouldering room," said John Wiygul, partner and general manager of High Point Climbing and Fitness.

Not counting the boulders, the complex will support up to 87 climbers at once, including some supported by so-called "auto-belays," which automatically take up slack in a climber's support rope without human intervention.

The project has ballooned by $2.5 million from its original projections, which called for a $4 million building. But doing something that's never been done before isn't easy, said Jim Williamson, vice president of planning and development for River City Co. Even finding a place for the 40-foot indoor climbing walls was a challenge.

"For this to be a premiere site, they need to be at least 40 feet," he said. "We only had 20 feet, and there are 600 cars above you so you can't raise the roof."

So they dug out the concrete floor -- an expensive, time-consuming process, but one that was a prerequisite to being taken seriously by the climbing community. The same pit can also be used to train emergency responders by inserting a length of drainpipe to simulate a well or other confined space into which a person might fall and require rescue.

While there are no estimates yet as to how many tourists the attraction would draw, The Block will certainly move the needle on the demographics of the Scenic City's visitors, said Dave Santucci, vice president of marketing for the Chattanooga Convention and Visitors Bureau.

"It will create something for families, and especially for those with teenagers," Santucci said. "This, combined with our natural assets, is a huge advantage."

Contact Ellis Smith at esmith@timesfreepress.com or at 757-6315