Is it a sculpture? A coffin? An alien pod from outer space that landed right at the 16th and Mission BART plaza? No, say BART officials, it’s actually a bench — a 3,900-pound, $4,661 bench — that was installed a couple of days ago on the northeast plaza near Walgreens.

“There are a lot of interesting things that happen at 16th and Mission,” said BART Board of Directors member Bevan Dufty, standing at the plaza Thursday morning. “So we might as well add this to the mix.”

Dufty explained that BART had to remove some seating roughly six months ago during the deep “thermocleaning” of the plaza. “We replaced it with some stone seating and that was fine, but then I had a couple of people say we could use more seating in the plaza,” Dufty said.

So, BART officials decided on the Factory Furniture “Camden Bench.” The Camden Bench, which can be found in numbers in front of Freemason’s Hall in London, has been described as the perfect “anti-object” and a “masterpiece of unpleasant design” — as it is designed to be a bench and a bench only.

The bench has a waterproof, anti-graffiti coating, no flat surfaces where liquids can accumulate, and no crevices. Its angles make it appear extremely uncomfortable to sleep on, and a challenge to skateboard on. You can sit here, but not do much else.

Dufty, formerly the city’s homeless czar, rejected the notion this emplacement was meant to deter homeless people from using it or sleeping on it. “This is not homeless architecture,” he said. “This is really something about seating that’s sturdy and different.”

“I think people can sleep almost anywhere,” he added. There was no “money-back guarantee” that people would not sleep on it anyway, he said.

Dufty said that if the bench is well-received, more could be installed at other stations.

Despite its status as the exemplar of unpleasant architecture, people who hang out at the plaza did not seem to mind its arrival — once they figured out what it was. “I didn’t know it was a bench,” said Louise Irish, a resident of the Mission Hotel only blocks away. She only realized what it was when she saw a friend seated on it. So she sat down, too.

Irish said it was comfortable enough to use while waiting for the bus or sit a spell after her trip to Walgreens. “It’s kind of interesting architecture,” she said

Jackie and CJ, who sometimes frequent the plaza, decided to pass. “What is it for?” Jackie asked, inspecting it. Once she was told what it was, she said: “It doesn’t even look like it’s worth sitting on because it’s so ugly.”

CJ said it was too high for him to use because of his bad legs and preferred the lower-lying benches facing 16th Street. “Why would I hoist myself up just to sit down?” he said. “Then I have to jump down to get off.”

Quincy “Q-Ball,” who said he lives on the plaza, sat near the bench and looked at it. “I like it,” he said. “It’s got that glow.” Like a new car, he agreed.

“It would look jazzier with some spray paint,” he said. He also said it would be better if it had a little built-in speaker for music.

Staring at it while seated on the curb, he said he’d try it out eventually.