The remains of a 6000-year-old dwelling have been uncovered during water mains construction work in Ayrshire.
Archaeologists found post holes, which formed part of a rectangular building, and fragments of Neolithic pottery near Hillhouse farm outside Kilmarnock.
The discovery was made recently as Scottish Water worked on an ongoing £120m project to upgrade pipes between Ayrshire and Glasgow.
It is believed the structure was built by some of Scotland’s first farmers.
Archaeologists said it was older than the Callanish Stones in Lewis and Stonehenge in Wiltshire.
Kenneth Green, of Guard Archaeology in Glasgow, described the discovery as one of the most important of its type in south-west Scotland in recent years.
He said: “Heavily truncated by millennia of ploughing, only the deepest parts of some of the post holes survived, arranged in a rectangular plan and containing sherds of early Neolithic pottery, hazelnut shell and charcoal.
“The width and depth of these post holes indicated that they once held very large upright timber posts, suggesting that this building was once a large house, probably home to an extended family or group of families.
“Up until this time, during the earlier Mesolithic period, Scotland was inhabited by small groups of hunter-gatherers, who led a nomadic lifestyle, living off the land.
“The individuals who built this Neolithic house were some of the earliest communities in Ayrshire to adopt a sedentary lifestyle, clearing areas of forest to establish farms, growing crops such as wheat and barley and raising livestock such as cattle, sheep, goats and pigs.”
The hall, which measured 14m (46ft) in length and 8m (26m) in width, is though to have formed part of house built by the first farming communities in Scotland.
Fragments of a Neolithic bowl, used for cooking and storage, were also found.
Scottish Water has been working with archaeologists to identify sites of potential interest along the route of the water main installation to allow the archaeologists to carry out excavations.
Scottish Water environmental adviser Andrew Grant said the company was “delighted” that something of such importance had been uncovered.