Emergency services were called when the woman vanished into a void outside a cafe on North End Road in Fulham, south-west London.
Passersby said they heard a loud scream and saw the woman had stumbled into the one metre hole.
The woman was taken to hospital but was not seriously injured, the BBC reported.
Local workers rushed to help when the woman in her 40s fell into the hole.
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The area around the hole had been blocked off with tables and chairs, in an attempt to stop people walking into it, nearby market stall holders said.
However, they added despite shouts by cafe staff, the woman who had a shopping trolley, squeezed through the chairs and fell down the hole.
Mohammed Atillah, who works in the cafe, said he was outside talking to the man who stumbled earlier, when the woman walked through the makeshift barrier and fell down the hole.
Atillah said he helped her to reach the floor of the basement under the cafe and she walked back up via the stairs.
The London Ambulance Service said: "The patient was shaken but not seriously injured and we took her to Charing Cross Hospital.