Historic Scotland is giving a limited number of visitors the chance to see first hand, and from an unusual vantage point, the conservation work at Glasgow Cathedral.
Visitors will scale the scaffolding on the outside of the cathedral, as experts talk about the work they are doing to preserve one of Glasgow's most notable landmarks.
The work to conserve the cathedral is an intricate, long-term project and this behind-the-scenes tour will explain the challenges facing the craftsmen.
It will include a visit to the stone masons' yard, where stones are carved to marry in with the existing stonework, and there will be a chance to learn about carving and installing a new gargoyle, window tracery and pinnacles.
Ian Lambie, Glasgow's District Architect, said: "The cathedral is a unique and glorious structure. Our craftsmen are matching the style of medieval masonry as accurately as possible.
"In doing so, they need to deliberate on how medieval masons would have dealt with movement and shifting in the building and plan for complex shoring to allow for the replacement of massive, original masonry."
A short talk will also be given on the history of the cathedral and previous and current works undertaken.
The ongoing project to restore the cathedral began in 2000.
Conservation work on the east end of the building was completed three years ago and work is continuing on the main façade and west front.
Glasgow Cathedral was built in the 12th Century. It was the only medieval cathedral on the Scottish mainland to survive the 1560 Reformation virtually complete.
It is said to sited on the spot where the patron saint of Glasgow, Saint Mungo, built his first church.
The tomb of the saint is in the lower crypt.
Four tours will take place on Friday September 27 and Friday October 4, each for a maximum of 12 people per tour.
Tickets, for over 18s only, must be booked in advance. They cost £20, or £15 for members of Historic Scotland.
For details and tickets, see log on to http://conservation.historic-scotland.gov.uk/home/future-events.htm