The oil well at the Beverly Center

“What’s that noise?” he asked. It was an electronic hum, omnipresent, not loud but impossible to ignore.

“It’s the oil well,” Poppy said. At Vish’s confused expression, she explained. “The mall is built around an oil well. They put up a barrier to hide it from the street, but it’s active.”

Vish glanced at the wall. “Is it safe to have a bar here?” he asked. “Wouldn’t there be all kinds of chemicals in the area?”

“Sure.” Poppy gestured with her chin at a multi-colored chemical hazard placard mounted on the bar. “It’s not like they don’t warn people. It’s probably fine, as long as you don’t lick the ground or anything.”

In Wrong City, Poppy Kang takes Vish to a secret bar accessible only through the parking structure in the Beverly Center, a monolithic mall on the eastern fringe of Beverly Hills. She mentions to him that the mall contains an oil well, located behind a big concrete mall.

It does. The Beverly Center is built around an active oil well. No word as to whether there's a top-secret, exclusive bar located next to it, though odds are unfortunately low.