Las Vegas promenade known as the Fremont Street Experience.
Lightning flashes over the Las Vegas Strip as a thunderstorm dumps rain and hail in Las Vegas, Nevada.
Las Vegas Mayor Carolyn Goodman said the thrill ride dubbed SlotZilla was destined to become an iconic city landmark.
"This is going to be known around the world: Come ride our Slotzilla," she said, standing beside showgirls and a scale model at the unveiling.
The monster zip line will cost $11 million to build and between $20 and $30 to ride. Construction is expected to start in January.
The attraction, expected to open in June, is an expansion of a much smaller, temporary zip line that has for two years scooted families, newlyweds and Elvis impersonators beneath a long metal canopy that displays an hourly light show.
That ride was intended to be a 30-day novelty, but it proved such a crowd pleaser the business community began working to make it permanent.
Currently, riders launch four at a time from a 67-foot (20-meter) metal scaffolding and land 800 feet (244 meters) away near the Four Queens casino, halfway across the pedestrian mall that features the world's largest video screen.
The new tower will be twice as tall, feature twice as many lines, and will look like a giant slot machine spitting out disoriented tourists.
With each new batch of zip-liners, the handle will dip, the wheels will spin, and the doors will open, revealing the course to the tourists on top.
"If you're going to do something here, you have to do it bigger and better than anywhere else," said Fremont Street Experience marketing director Thomas Bruney.
Officials are betting the new attraction will lure more visitors the downtown area, which has struggled to compete with the flashier Strip three miles (less than five kilometers) away.
It is intended to reflect the "vintage Vegas" vibe that characterizes the promenade, nicknamed "Glitter Gulch" for the classic casino signs that glow amid the souvenir shops and buffet signs.
Riders will be able to stop halfway, or continue to the end of the 1,700 course, landing near the Golden Gate casino. They will have the option of flying along the lines in a horizontal "superman" position, and accelerating their ride using a new "power launch" system.
Bootleg Canyon Flightlines operates the current ride. The new structure will be built by the Hawaii-based company Skyline, better known for zip lines that span waterfalls and forests.