Heavy rainfall has caused a moat to form around a 4,000-year-old prehistoric hill.
Silbury Hill in Wiltshire now resembles an ancient fort after downpours led to a large horse-shoe shaped lake forming around it.
The 40-metre chalk site at the Avebury World Heritage Site is the largest artificial mound in Europe, with archaeologists knowing little about its purpose.
But it is believed to have been built by hand and taken a lot of workers to complete.
Tim Daw, local expert on ancient monuments, told BBC Radio Wiltshire it is possible when the mound was built it featured the moat as a permanent feature.
He said: "Back when they built Silbury Hill and Avebury, researchers say, the water table was higher, perhaps two to five metres higher, so there would have been a lot more water about.
"So maybe we're actually seeing with this rain and higher ground level of water, because it's been a little bit damp, more what the original builders intended [the hill] to be like."
English Heritage's senior properties curator Win Scott said the moat is known to form seasonally and will naturally drain away over time.
He added: "It [the water] has appeared there for at least 4,000 years and was partly created by the digging of turf and chalk for the construction of the great mound,"
Flooding at the site has occurred most recently in 2000, 2007 and 2013, and does not prevent visitors from viewing or accessing it.
October one of the wettest ever in the UK
The UK experienced more a third more rain than average, with a total of 171.5mm, in what was provisionally the joint-sixth wettest October on record, the Met Office said.
It came after Storm Babet caused disruption across the UK.
Eastern Scotland had its wettest October on record in figures that go back to 1836, with 235.9mm of rain recorded, 82% more than its average.
The counties named by the Met Office which recorded their wettest October on record included Angus, Dundee, Fife, Kincardineshire, Staffordshire, Nottinghamshire, the Isle of Wight, Armagh and Down.
Northern Ireland had its fifth wettest October on record, with the 191.8mm, 68% more than its average.
England had its eighth wettest on record with 147.2mm of rain, which is 63% more than average.
Storm Babet’s impacts on England and Wales were mainly felt from 18-20 October, in what was the third wettest three-day period for England and Wales in a series from 1891, while the Midlands provisionally recorded its wettest three-day period on record.
Met Office senior scientist Michael Kendon said: “Despite some warmth in the south early on, October 2023 overall goes down as a wet month for much of the UK, with some areas seeing record-breaking levels of rainfall."
The storm claimed the lives of seven people in Britain, including three in Scotland.