Archaeologists have discovered a 2,000-year-old water main built by the Romans - which is still working.
The pipes took water from a nearby spring
The find has amazed experts at the Vindolanda Roman fort in Northumberland.
During ongoing excavations at the site, workers discovered a 100ft stretch of wooden mains, which at one time fed the fort with water from nearby springs.
The pipes were constructed by drilling large lengths of alder, which were joined together by oak pegs.
They were found under the floor of what is thought to have been an area used as a hospital in about 100AD.
Experts believe the network of pipes fed spring water to individual buildings within the fort.
A spokesman for the Vindolanda site said: "The fact that they were still working is quite incredible, but it was also a nuisance because they flooded the excavation trenches which had to be pumped out every day.
Women and children
"The finest of the surviving timber was the wooden water main, which ran across the site, being associated with the earliest occupation there.
"Large alder trunks, with bark remaining, had been bored through with an augur, to create a 5cms pipe for the water and the individual lengths were connected with rectangular oak slabs, without any use of iron or lead fittings.
"The source of the water was probably the major spring at the western edge of the Vindolanda site."
The dig has also uncovered a total of 238 boots and shoes - and half of them belonged to women and children.
Vindolanda become famous through the discovery of about 1,700 examples of writing tablets, which give a remarkable insight into life on the Roman frontier.
Now, with the backing of the Heritage Lottery Fund, the Vindolanda Trust has bought 15 acres of farmland adjoining the fort.
The new land doubles the area available for excavation.
About 800 people lived on the site for 350 years and it is thought the original 13-acre site will take another 150 years to excavate.