It was the radical business venture that harnessed Bath's history as a healing spa city and blended it with the well-documented health benefits of hearty sea air.

But now the UK's first therapeutic salt cave is up for sale after the phenomenon that proved a hit in Central Europe failed to catch on here.

Constructed using salt crystals from the Wieliczka salt mine near Krakow, Poland, the unique ground- level cavern in James Street West was a labour of love for Bartek Filinski and his sister-in-law Danuta Kotarska.

Designed to alleviate a range of respiratory and skin conditions, including asthma and psoriasis, and to reduce the effects of stress, it uses a 'halotherapy' air-conditioning unit which pumps salt particles into the atmosphere as customers relax in deckchairs.

Mr Filinksi, 28, said just three-quarters of an hour of simply breathing in the room is equal to “three days at sea”, thanks to the iodine, bromine, magnesium, potassium and other minerals said to have antibacterial and antiviral properties.

Although the technology is fairly new, salt spas have their origins in the 19th century, where investigations revealed that Polish salt miners had healthier lungs than other people.

Mr Filinksi hoped that, like Bath's Thermae spa complex, his salt cave would prove a hit with tourists and health-conscious Bathonians alike. So he poured thousands of pounds into importing crystals and constructing a soothing grotto next to his Polish delicatessen.

But unlike their home country, where there are 200 such spas and up to 50 customers often sit shoulder-to-shoulder among the back-lit salt rocks and plaster stalactites, it has failed to secure enough bookings to survive.

Mr Filinski said it was with huge regret he has to sell up, just one year after opening. He said: “It is such a shame but I am trying to run two businesses and it has become a worry for me.

“At the beginning, it was new so people called and visited, but that has tailed off and the Polish population in Bath is forever changing and people don't stay here long.

“My hope is we might be able to open it up as a restaurant or bar as we have quite a lot of extra space to expand and, although we'd take the salt stones off the floor, we would keep the interior as it is, so it was a bit different.

“But I would really prefer it if it could continue as a salt cave and I am hoping somebody who has more time to give to it can take it on.”

Mr Filinski, who runs his deli with his father, believes a lack of knowledge about the cave's health benefits could be the problem.

“People are surprised when we say you just come in and sit, but all you need to do is breathe in and then we play soothing music,” he said.

“Maybe if I had more time to educate people about it and promote it, it would have been different.

“Crystal salt is a natural ioniser which improves the air quality by emission of negative ions, which are in huge concentrations in seaside air.

“Negatively ionised air enhances health and supports treatment of many ailments. In Poland, there is a salt cave in every spa city and they are always busy. “It is particularly beneficial for children or the elderly and doctors regularly recommend the caves to people.”