Twenty St Albans residents have been evacuated from their homes after a 66ft sinkhole appeared on their street.
The massive opening occurred in Fontmell Close in St Albans, about half an hour from London.
Six families have been put into temporary accommodation as officials try and find out if their homes are safe to return to, with fears that the sink hole has made structural damage.
A smaller hole was reported in the street last week, but the sinkhole then opened up in dramatic fashion earlier today.
Hertforshire council said in a statement: "We were informed about a hole in the footpath last week. It was inspected and barriers put around it on Monday.
"Work was scheduled to fill it in this morning. Following our inspection, there was no reason to suspect that the hole would collapse."
Luckily, nobody has been injured from the sinkhole, but one neighbour claims they saw a postman injuring himself on the smaller hole last week.
Local resident Steven Lynch told the BBC"My wife saw the local postman pulling himself pretty much out of the hole and dusting himself down... he was rolling around on the street looking quite badly injured."
"The return to normal is likely to take weeks and all agencies in Hertfordshire are working together to support families affected.”
Another resident Abu Newbigging, 38, told the Mail Online that she had been told to leave her home.
She said: “We are without power and gas and water and sewage and the council are advising people not to stay.”
Sinkholes occur when rock has been dissolved by water, with limestone, gypsum and chalk all ground substances vulnerable to eroding.
They are still a rare occurrence, and worried residents are encouraged to speak to their council for more information.