The ominous and macabre structure may have frightened some hikers on the Long Mynd, near Church Stretton in south Shropshire.
But there is nothing to fear, according to landowners the National Trust.
It says the gallows are simply a film prop that had yet to be taken down.
The rudimentary wooden hangman-style structure was in fact a mock gibbet, of the kind criminals would have been strung up on as a warning to others in some of the less civilised periods of history.
A walker, who did not want to named, said they had come upon the chilling sight when walking over the heathland at the summit of the Long Mynd.
She said: "There is a structure today in the top of the Long Mynd at Church Stretton, on the Pole Bank walk, which wasn't there 48 hours ago and is causing passers-by some considerable concern and anxiety."
However the structure wasn't real, nor intended to frighten anyone, said Peter Carty, countryside, parkland and gardens manager for the National Trust in south Shropshire.
Mr Carty said that it was simply left over from a day of filming on Thursday with Fiery Flying Films Ltd, a company based in Battlefield, Shrewsbury.
He said: "There has been a film company filming up there, they have been doing just one day's filming.
"We talked to the graziers and they are all OK with it, and the crew have had stewards on site to explain to people what is going on."
He added: "I thought we had all bases covered.
"The scene was somebody hanging in a gibbet and two horse riders coming towards them on a desolate heath.
"As to what the film is about I couldn't tell you.
"What we agreed is that if people want to walk through they would have to stop filming, but it seems most people have been happy to just walk around the site."
He said the film makers had paid a fee for the use of National Trust land, which will go into the body's coffers to help fund future conservation and other activities on the Long Mynd.
The film is to be called Fanny Lye Delivered, and is described as a 17th century drama directed by Thomas Clay and starring Maxine Peake and Tanya Reynolds.
"Gibbeting", or the placing of condemned criminals inside a metal cage hoisted from a gallows-like structure, with them often left to starve to death, took place until the 17th century in Europe as a form of punishment and a deterrent.