Hidden tunnels last used as World War II bomb shelters are to be opened up in Cardiff Castle as part of a major refurbishment scheme.
Work at the castle is expected to take five years
The Heritage Lottery Fund is financing a £6m renovation effort - currently Wales' largest conservation project.
Work is estimated to take up to five years to complete, opening up to the public a series of tunnels running around the castle for the first time in more than 50 years.
Internationally acclaimed stone masons have been drafted in to re-point the walls surrounding the castle - which include the remains of Roman work.
And a number of improvements are being made to the main house including access for disabled people.
The castle's wine cellar is planned to be opened to the public for the first time complete with the presses and vats which were last used to make Cardiff Castle wine in 1914.
Scaffolding has been erected around the exterior of the castle but a series of photographs featuring scenes from inside the house are planned to be hung on the outside of the castle walls.
John Edwards, who is leading the project said the work was part of a long term strategy to preserve the castle.
"At the moment we are working on the masonry and have carried out detailed research over the last 18 months in order to make sure that the work is sensitive to the castle," he said.
"We have consulted with international masonry experts for this phase of the work who are working here at the moment.
Stone masons have been drafted in for improvements
"We are going to be working on the tunnels which go right around the site.
"At the moment only about 15% are open to the public, but we hope that 100% will be open when the work is completed."
"They were last used as shelters during the war," he added.
"We are also planning to open the wine cellars and who knows we may even start wine production again," he joked.
As part of the restoration scheme, Professor John Ashurst and master mason Colin Burns are leading a team of skilled masons to work on the walls of the castle.
Prof Ashurst said: "This has to be one of the most interesting projects we have worked on."
As well as seeing the attractions within the castle visitors are being invited to see the expert masons at work on the restoration.