NONE OF THEM knew the color of the sky," Stephen Crane might have written. For who among the quarter-of-a-million upward-gawking strollers across the Leonard P. Zakim/Bunker Hill Bridge was looking at the murky sky rather than at 116 glistening white cables? Sail-rigging? Harp-strings? A breeze blowing open the pages of a book? For the first and last time, the spectacular symbol of the new Boston, a "Colossus of Roads" (as my friend Calvin calls it) astride the gateway to the Charles River, was open to pedestrian traffic, thanks to the Massachusetts Turnpike Authority Central Artery/Tunnel Project and its volunteers, and WalkBoston (the country’s first advocacy group "to raise public awareness about the benefits of walking").

The bridge opened at noon, and people on the line, who had started arriving around nine, were already enjoying the event, checking out the old rusty supports that would soon be only a memory. A few raindrops came just as I got to the bridge entrance. Would we be told to go home and return on the rain date? No way! Even as the precipitation precipitated, no one was about to give up. Dunkin’ Donuts distributed free plastic hooded slickers. There was a checkpoint, but the crowd had followed the advance advice about leaving backpacks at home — so no one was being searched, though I caught a trio of drunks being "interviewed" by security.

In the crowd, I ran into two colleagues from UMass Boston and a soprano friend who requested "a kiss under the crotch" (already a nickname for the undersides of the two 10-lane-spanning arches); I was happy to oblige. Behind the ropes on both sides of the northbound lane (the only lane open), Turnpike Authority workers and engineers, spaced every few yards, answered questions and gave advice to photographers, some of whom were allowed to snap their shutters from off-limits. Applause greeted Waltham’s renowned American Legion Band, who played marches from scores kept dry under clear plastic (later, Roy Nutile’s 16-piece swing band, from Needham, took over). T-shirts were sold and picture postcards were distributed, along with little round orange stickers that read, i walked the big dig bridge may 12, 2002.

The rains came, but the crowd increased. Even unfolding umbrellas couldn’t interfere with the photo opportunities. The twisting, crisscrossing cables, with their upward Op-Art sweep, the holes that let sunlight through the sides of the road so the fish below won’t grow disoriented, and the great sexy arches are memorable sights — and will probably cause a few rubber-necking accidents once northbound vehicular traffic begins at the end of the year. By the time I left the bridge (and no one was hurrying anyone off), the rain was falling harder, but the line on the Charlestown side was at least four times longer than when I arrived. The only sour note came from the horns in the stalled traffic heading for the Celtics game at the FleetCenter. They shoulda taken the T.