SAN FRANCISCO -- A winter fantasy came alive Thursday -- thanks to several tons of trucked-in snow -- as Olympic ski champ Jonny Moseley and his buddies transformed one of the steepest streets in San Francisco into one of the strangest king-of-the-hill competitions yet.

On two blocks of Fillmore Street, a section so steep that the sidewalks have built-in staircases, Mosely drew a big crowd on the gorgeously sunny day, and their aerial tricks as they soared across Vallejo Street had them cheering.

The disruption did not amuse some residents of the well-to-do Pacific Heights neighborhood, but Mayor Gavin Newsom blessed the event as a San Francisco original (he's big on those things).

"It's the old adage, 'Nothing ventured, nothing gained,"' said Mayor Newsom. "While this is unique, we consider ourselves unique."

Moseley, the 1998 Olympic gold medal winner in moguls, beamed with pride as he dug his heels in the snow, helped erect retaining walls, and oversaw the growing contour of the slope.

"It's about 14,000 cubic feet. That's my number," Moseley said as he helped staple up some banners promoting sponsors of the event, which was organized by Icer Air, a ski equipment company. "We've got plenty. We're good."

But any air was caught, there had to be a wedding first. Bill Parker and Tracy Daily were wed halfway down the jump in a ceremony that featured Moseley skiing with the bride.

"After it was canceled the first time, we wrote Icer Air," explained newlywed Daily. "They responded immediately."

"(Moseley) is just a really cool guy," said Wyatt Daily, son of the bride and best man in the ceremony.

After the wedding party cleared out, some of the world's top snowboarders and skiers made their way out of a trolley car parked on Broadway, hit the jump at Vallejo Street, and landed with precious little space to spare near Green.

It took a few trips down the 400-foot run before they hit their stride. The first jumpers came up a bit short, banging into massive Styrofoam blocks short of the landing area. That elicited a nervous murmur from the sun-drenched crowd. The heat had softened the snow, and while the street plunges down a grade of more than 18 percent, that's not as steep as the slopes these world-ranked skiers and snowboarders were used to.

The thousands of spectators clearly enjoyed watching them fling themselves skyward in the middle of the city.

"In San Francisco, you learn to expect that anything will happen," said one city resident, Theresa Smith. "It's out of the ordinary for something unusual not to happen."

"I think this is following in a long line of great San Francisco nuttiness," said another, James Armstrong.