A heavyset woman caved through an Upper East Side sidewalk last night — dropping six feet into a huge hole where she was eventually pulled out by emergency crews using a crane-like rescue unit, authorities said.

The 31-year-old Queens woman was huddled up against the wall of Atomic Wings at the Blue Room Grill on the corner of East 60th Street and Second Avenue, seeking shelter from the rain while waiting for a bus, when the sidewalk below her gave way around 9:15 p.m., witnesses said.

“The woman was enormous. She had to be more than 300 pounds,” said Daniel Crumity, 44, of Queens, who watched in disbelief from a window inside the Blue Room. “The ground literally fell out from underneath her.

400-POUND WOMAN SAYS HER SIZE SAVED HER LIFE

“It happened so fast she did not scream or anything. Everybody in the bar got up to look.”

She was taken to Cornell Hospital where she was treated for shoulder injuries and listed in stable condition.

The woman fell straight through the concrete into an area below that appeared to lead to the restaurant’s basement, witnesses added.

FDNY Fire Chief Thomas Jemmott said the woman had to be pulled up in “high-angle rescue unit” resembling a crane with cargo netting.

“Pretty sophisticated stuff,” he said. “She is a very large person, but we were able to secure her and stabilize her and lift her out of the hole.”

Messages left with the city’s Buildings Department and Transportation Department went unanswered.