Families in Bath had a lucky escape when heavy rain dislodged a boulder-sized piece of wall just behind their homes.
Torrential rain caused the mini-landslide, which saw the three-tonne boulder fall in Camden.
Residents were woken at midnight by a loud crashing sound, and police were on the scene straight away.
A structural engineer from Bath and North East Somerset Council was called to the scene, which is in the grounds of the offices of risk analysis specialists Maplecroft in St Stephen's Road.
Bob Williams, whose house backs on to the road, said: "I was woken by a huge rumbling crashing sound, which I was very puzzled about.
"I looked out of the window, but it was too dark to see anything, then the police knocked on our door to let us know what had happened.
"I was worried about the house, especially as I have a four-year-old.
"This is a well-used road and it is so lucky that no one was walking there when it happened.
"We were fortunate that our house suffered no damage. There was just a bit of rubble that reached us and pushed open our garden gate."
Gary Lock, whose house also backs on to the road, had parked his car near where the boulder landed on Thursday night. He said: "My car suffered some damage when the rocks fell. I heard the noise, and came out to investigate. Then I decided to move my car in case any more rocks fell.
"We were very lucky that our house was not damaged and it is so lucky that no one was hurt."
The incident blocked the front entrance to the Maplecroft offices.
Spokesman Ed Cole said the incident was not a landslip and that the stone was part of a retaining wall that fell away because of the heavy rain.
He said: "This is the collapse of a retaining wall, which gave way in part. It's not structurally unsound because only part of it came away. I think it was a build-up of water behind it.
"The council was very quick to respond when it happened and have been back to extend the safety barrier and make an assessment of what needs to happen next and how we make the whole bank safe."
Mr Cole said scaffolding had also been put up around the remainder of the wall.
The incident has revived memories of a tragedy in 1969 in the same area of the city, when a six-year-old boy was killed in a landslip.
Rutherford Place resident Hilary Fraser, who has lived in the area for 50 years, said: "It may seem a long time ago but for those who can remember it was a terrible incident and cannot be repeated."
A spokesman for B&NES said members of its building control team had installed a retaining barrier to prevent further masonry falling down the hillside, and was now in discussion with the insurers of the affected properties.
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