People having sex on top of the Oxford Castle Mound - one of the city's scheduled ancient monuments - have been warned their amorous antics could be captured on CCTV.
The Mound, which dates back to the 11th century, opened to the public for the first time in June, as part of the £40m Oxford Castle development.
In May, the Queen opened the site in New Road, including the £20m transformation of the former Oxford Prison into the Malmaison Hotel.
The following month, Oxford Preservation Trust opened Oxford Unlocked, a heritage and education centre which examines the history of the site.
The preservation trust charges £1 admission for a walk up the Mound, and staff in the Oxford Unlocked shop said on Monday they were sometimes forced to clear up after courting couples.
One member of staff, who asked not to be named, said: "There is no evidence that people are taking drugs up there, but we know some of them are having sex because we have to clear up in the morning."
Trust director Debbie Dance said: "Some people warned us that the Mound, which is one of English Heritage's scheduled monuments, would be abused, but our findings are that this is generally not the case.
"CCTV coverage is live, and the path going up the Mound will be lit up from September 21, so we would ask people to take care of it and not abuse it.
"People are beginning to look after it, and be proud of it, and the view from the top tells the story of how early Oxford developed.
Emily Hirons, operations manager of Oxford Castle Unlocked, which controls entry to The Mound, said the monument was only open between 10am and 5.30pm, seven days a week.
She warned people scaling The Mound at night that they could be caught on camera but added that couples climbing the hill to have sex was not a "regular occurrence".
She added: "Our staff are managing the Mound, and this is certainly not happening during the day.
"We have had a brilliant summer - it has been very busy, with lots of visitors."
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