Visitors to the Neolithic village of Skara Brae on Orkney will be offered a glimpse inside the ancient homes for the first time on Saturday.
The 5,000-year-old buildings can normally only be viewed from paths around the site, to aid preservation.
The tours, arranged to mark World Heritage Day, will visit the settlement's workshop, main passageway, and three of its ten houses.
Rangers at the site said there had been no public access since the early 1970s.
Elaine Clarke, of the ranger service, said: "This is a rare opportunity to go inside the houses which were built by these early farmers.
"To get close to the fires where they cooked, the beds where they slept and the shelves where they stored their precious items."
She said the chance to view mysterious carvings on the internal walls of the complex would be a highlight of the tour. The meaning of the etchings, comprised of lines and geometric shapes, remains unknown.
Demand for the limited number of tour places available had been overwhelming, she said.
It is hoped the event will help to promote conservation of the historic site.
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