Denbigh Castle is to undergo a £600,000 revamp, including a new visitor centre.
The custodian, Welsh heritage body Cadw, wants to maximise the visitor potential of the 13th Century castle, which overlooks the Denbighshire town.
It also plans to open up more of the historic walls around Denbigh, giving access to walkers, and providing guided tours.
The castle is due to close next month to allow work to get under way.
Work on the castle began soon after Edward I created the Lordship of Denbigh, which he granted to Henry de Lacy, the Earl of Lincoln, in 1282.
Much of the castle, the town walls, and other historic features still remain, according to county archaeologist Fiona Gale.
From next February when the castle reopens, Cadw wants to make the building a "key heritage visitor attraction", according to Heritage Minister Huw Lewis.
He said: "It's an exciting development for the community of Denbigh, and Cadw's development at the castle will tie in very well with the work undertaken by Denbigh Town Council to develop and promote the historic town's heritage and tourism value."
Last year, the town council helped set up a scheme where volunteer guides offer visitors a tour of the town, sharing its history and providing an insight into its 235 listed buildings.
In all, 19 guides "graduated" with an assessment from the Blue Badge tourist guides.
Sharon Braunton, Denbigh community reporter for BBC Radio Wales, helped set up the guides group with money from the Heritage Lottery Fund.
She said plans for the visitor attraction were "amazing", adding that she was looking forward to seeing more of the historic walls opened up to visitors.
The plans include a purpose-built visitor centre, as well as improvements to the "presentation and interpretation of the monument and walls, and links with the wider historic landscape of Denbigh".
The castle will close its doors on Sunday, 24 July and is due to reopen on Monday, 6 February next year.