Plans to restore a ruined medieval castle have been unveiled.
Abseiling engineers are surveying Corfe Castle keep
The National Trust and English Heritage plan to restore the top section of Corfe Castle - at a cost of £700,000 - to allow public access again.
The top part of the castle was closed after frost damage and crumbling stonework prompted health and safety fears in April this year.
The 1,000-year-old monument near Wareham, Dorset, attracts more than 100,000 visitors each year.
Pippa Russell, visitor services manager at the castle, said: "The ravages of time have begun to catch up with the large pieces of stonework around the keep, many of which lie on their side or upside down where they fell when the castle was blown up by gunpowder in 1646.
"The inner core of these sections is more exposed to the elements than standing walls and this is where much of our remedial work will be focused."
The two-year project will see the capping on top of walls replaced, the original plasterwork in the keep restored and loose sections of stonework pinned back.
The first phase will begin next month.
The fortress has had a troubled history and was thought to have been an important Roman defensive site.
Henry III constructed additional walls, towers and gatehouses, while Queen Elizabeth I sold it to Sir Christopher Hatton, her dancing master and supposed suitor, in 1572.
By 1643 the Parliamentarians occupied most of Dorset, and the castle then survived a six-week siege, followed by a number of blockades, and a second siege started by Colonel Bingham, Governor of Poole.
The castle was then betrayed from within and the Roundheads took over in February 1646.