32-year-old Ulanda Williams from Queens, New York . . . who clocks in at a mouth-watering 400 pounds . . . was in Manhattan, waiting for a bus, and huddling against a wall to shelter herself from the rain.  And suddenly, the sidewalk GAVE OUT.

Turns out she was standing on a piece of sidewalk that was built over a restaurant's basement.  The basement didn't have a ceiling in that area, just the sidewalk tile.  So when it cracked, she fell seven feet STRAIGHT DOWN into the basement.

The fire department had to use a CRANE and a CARGO NET to get her out.  A fire department official told reporters, quote, "She is a very large person, but we were able to secure her and stabilize her and lift her out of the hole."

Fortunately, Ulanda only suffered a broken arm.  And she says her girth SAVED HER LIFE.  Doctors told her a thinner woman could've DIED in that fall.