It is not known when Berkhamsted Castle will reopen after being closed due to flooding when its moat filled up with rainwater, blocking off all access points to it.
Site-manager English Heritage has only said it will be closed ‘until further notice’ as high water levels have made it unsafe for visitors.
A sign informing people of the news is on the closed gate to the castle and on the English Heritage website.
John Waller, 70, of Cobb Road, Berkhamsted, said: “People come from all over the world to go to Berkhamsted Castle and then they cannot get in.
“It’s understandable – because of all the rainwater there, but I do hope something gets done about it soon.”
Mr Waller gives tours of the castle to schoolchildren and history enthusiasts.
The sign on the castle’s gate says: “Due to high water levels, for your safety, the castle grounds will be closed until further notice.”