Residents had to be evacuated after a 66ft (20m) sinkhole measuring 33ft (10m) deep opened up in a suburban street in St Albans.
Hertfordshire Fire and Rescue Service tweeted this picture showing the scale of the hole which swallowed up a big chunk of ground and part of a wall.
Cars parked on locals driveways are now blocked in and more than 50 properties are without gas and electricity which were cut off as a precaution.
The fire service said it was already aware of a small hole on Wednesday which was due to be filled in.
But it then received a call at 1.30am to say it had "opened up substantially" overnight.
A Hertfordshire County Council spokesman said: "Holes of this kind crop up across Hertfordshire often for historic reasons.
"We’d like to reassure the public that it is rare for them to turn into large holes.
"No one has been injured and no house has been damaged.
"The return to normal is likely to take weeks and all agencies in Hertfordshire are working together to support families affected."