The castle is protected by strict rules governing development
A 13th Century ruined castle is to be sold, with a starting price of £80,000.
Ewloe Castle, built by Llywelyn ap Gruffydd, is to to be auctioned with four other lots which are expected to fetch more than £500,000 in total.
Although privately owned, the castle is under the custodianship of Welsh historic monuments agency Cadw, and its character "must be preserved".
The auction will be held at the Beaufort Park Hotel in New Brighton, Flintshire, on 8 December.
Estimates as to the castle's origins vary, but it is thought to have been built around 1257, as a hunting lodge for the Welsh prince Llywelyn ap Gruffudd.
It stands close to the site where 200 Welshmen, led by the king of north Wales Owain Gwynedd, ambushed - and nearly killed - King Henry II in 1157.
Agents Strutt and Parker are offering the site for sale, which includes 16 acres of pasture and 8.5 acres of woodland.
The agents expect the lot to fetch "in excess of £80,000".
The castle is now a ruin, and Flintshire Council said there were strict guidelines in place to restrict development and preserve the building's character.
Andy Roberts, head of planning policy said: "Given the rural location of the castle away from any settlement, the land which it occupies and surrounds it is designated open countryside in planning terms, with much of it also being green barrier which adds to the protection of its open character from development.
"The site of the castle and some of the land around it also has environmental designations which provide added constraints on development, and of course it is a scheduled ancient monument, whose character and setting must be preserved and protected."
A Welsh Assembly Government spokesperson said: "Ewloe Castle and its immediate area is in the guardianship of Cadw on behalf of the Welsh Assembly Government and is protected as a scheduled ancient monument.
" Because the castle is in the guardianship of Cadw, this means that the public would still be able to access the castle.
"Public access to the castle is via a public footpath."