It’s hard to believe San Francisco was once known as the City That Knows How, a nickname bestowed by President William Howard Taft in 1911. Just five years after weathering a devastating earthquake and fire, San Francisco agreed to host a World’s Fair in 1915. And it did so with aplomb.

All of that know-how seems to have vanished. Our Millennium Tower is sinking, leaning and spontaneously cracking — one window, at least. Our new $2.2 billion Transbay Transit Center has been open only a month, and the walkway around its rooftop park is already crumbling. Muni’s effort to repair the Twin Peaks Tunnel resulted in a citywide bus meltdown and the death of a worker.

San Francisco has so little know-how these days, it can’t even do the most mundane tasks well, like keeping a BART station plaza clean.

You may recall that Supervisor Hillary Ronen and Bevan Dufty, a member of the BART board, spent every Wednesday morning for months cleaning the plazas at the 16th Street Mission Station because nobody else seemed to bother. They pulled on plastic gloves and wielded brooms to deal with the heaps of trash and human waste — and even a dead pigeon. They called themselves, fittingly, “partners in grime.”

Finally, BART pledged to schedule two full-time janitors at the station and power-wash it every night. Ronen and Dufty stopped cleaning in March, figuring they’d made their case.

Recently, they started hearing the same old complaints about the plaza, and on Monday morning they ventured to the station to check it out. Ronen called me, livid.

“It looks worse than when Bevan and I started. I feel like I was lied to,” she said. “This, to me, is pure incompetence. ... I’m afraid somebody is going to get a disease from touching anything. We’re both just losing our minds.”

She described an unbearable stench, slum-like conditions with people sleeping on cardboard, heaps of trash, puddles of urine, pigeon poop caked on the ground and “brown yuckiness blobbed over the elevator.”

She sent me photos, which thankfully weren’t scratch-and-sniff, and fired off an angry letter to BART General Manager Grace Crunican.

I went out there the next morning, and while it had clearly been improved a bit after Ronen’s letter, it was still pretty dire.

The ground was littered with empty liquor bottles, broken glass, needle caps, cigarette butts and a Flamin’ Hot Cheetos bag. The brown yuckiness had been wiped from the elevator, but a stain remained. The areas around both escalators were filled with trash, including a single black shoe, and smelled like urine. At the bottom of the escalators sat more trash, including an empty cup that held instant noodles rolling around right next to garbage cans.

You know the worst part of this sordid tale? This, apparently, meets BART’s standards.

“BART is doing exactly what was agreed upon earlier this year,” Alicia Trost, spokeswoman for the agency, wrote in an email.

She said that, as promised, two workers clean the station every weekday — one from 6 a.m. to 2 p.m. and one from 2 to 10 p.m. She said that on weekends, one worker is split between the 16th Street Station and the 24th Street Station.

She said a contractor power-washes the 16th Street Station every night for one hour and that a new contract will raise that to four hours in October. In addition, BART is installing a new surface in the plazas that will repel liquids and be easier to clean.

Neither Ronen nor I saw any janitors at the station when we visited, though supposedly one had been working for a few hours by the time we got there. Something seems amiss.

At least San Francisco isn’t putting on a World’s Fair anytime soon. Surely, its buildings would lean, its walkways would crumble, it would be littered with needles and trash, and the whole thing would smell like a gas station restroom.

Understanding homelessness: Thankfully, there are still some folks in San Francisco who are capable and cutting edge — they just don’t work in government.

Loyal readers know I’m a big fan of Lava Mae, the nonprofit that turns decommissioned Muni buses and trailers into mobile restrooms and shower stalls for homeless people. Lava Mae has also branched out into art exhibitions intended to make viewers understand the lives of homeless people.

If you’re free Sunday, check out the final day of the group’s exhibition “Coming Home” at Proxy, the two-block outdoor space at 432 Octavia Blvd. Created by artist John Craig Freeman and sound artists Tania Ketenjian and Philip Wood, “Coming Home” uses iPads to overlay augmented reality scenes of homeless people and their recorded voices telling their stories.

From 4 to 8 p.m., they’ll have special events alongside the exhibition, including a station for making hygiene kits for homeless people, a sock and underwear drive, and Lava Mae bus tours.

Amy Schoening, Lava Mae’s curator of arts programming, said the exhibition is are intended to bridge the sometimes big gap in understanding between people who have homes and people who don’t.

“Can we get people to simply see each other?” she asked. “To not have that level of invisibility?”

Happily trapped: Despite all the serious and gut-wrenching issues in San Francisco, there are still lots of goofy ways to have fun in the perennially wacky city. And now that summertime tourists have left, along with Karl the Fog, it’s a good time to take advantage of them.

I’m teaming with Peter Hartlaub, The Chronicle’s pop culture critic and my partner in #TotalMuni2018, to come up with a list of the best tourist traps in San Francisco that are fun for locals, too.

We started the conversation with food editor Paolo Lucchesi on an episode of Hartlaub’s podcast, “The Big Event.” Lucchesi copped to enjoying a cocktail at the Cliff House bar. I am not embarrassed to say I love riding the (overpriced) cable cars and walking across the Golden Gate Bridge.

Hartlaub started a veritable firestorm by suggesting the Hard Rock Cafe at Pier 39 should be on the list, an assertion with which Lucchesi and I not-so-politely disagreed.

We ventured there for lunch the other day to see for ourselves and had the good fortune of meeting Diana Smith, who’s been a waitress at one Hard Rock or another for 34 years. She’s met Joe Montana, Mel Gibson, Phil Collins, Cyndi Lauper and more underdressed and freezing tourists than she can count.

“We get people from all over the world,” she said. “It’s upbeat and fun.”

Service? Top-notch. Food? OK, but overpriced. Among the best tourist traps in San Francisco? No. Sorry, Peter.

What are your favorite tourist traps, the ones you’re not afraid to admit you love? After we come up with our final list, Hartlaub and I will spend a day visiting some of them — sans the white tennis shoes, shorts and “I Escaped From Alcatraz” T-shirts, of course.

We’re aiming for Sept. 26. We’re thinking the day will include Irish coffees at the Buena Vista. We’re thinking you should join us. Stay tuned!

San Francisco Chronicle columnist Heather Knight appears Sundays and Tuesdays. Email: hknight@sfchronicle.com Twitter: @hknightsf