It isn't just the location, on the ground floor of a square 1970s building in a modern part of Bath, far from any natural geological feature.
Nor is it just the touch of Disney in the appearance – it is lined with pink, white and grey translucent salt rocks lit from behind and patterned like Palaeolithic paintings, with plaster stalactites on the ceiling and a water feature to one side.
No, for me, the oddest thing was the deckchairs. They looked out of place in the sombrely lit room, so far from any sunshine. "But they were really comfortable," one customer told me later: a frazzled mother from York who booked a 45-minute session with a friend for a bit of pampering.
The chairs were nearly my nemesis. A CD of repetitively calming music came on, the lights behind the salt rock panels became more intense, and gentle snoring filled the room as my companions-in-salt dozed off, tucked up in large blankets in case we got cold in the salt-air micro-climate that would swirl around us for the next 45 minutes.
But I couldn't work out how to recline my deckchair. I tried standing up and tipping it, but the only way was by launching myself in at a jump, risking a topple into the water feature.
I compromised by sitting slightly tipped, with the blanket tight around me, feeling like an old lady on a trip to the sea in a bathchair.
And I gently drifted off, dreaming of the ocean. Which was the right kind of dream: 20 million years ago, the chunks of pink salt chippings around me were part of a great shallow sea, now found in deposits between 10 and 300 metres beneath southern Poland.
A "speleotherapy" air-conditioning unit rumbled away, pumping salt particles into the atmosphere as I dozed.
Three-quarters of an hour in its presence is "equal to three days at sea", apparently, thanks to the iodine, bromine, magnesium, potassium and other minerals said to have antibacterial and antiviral properties.
Although the technology is less than 10 years old, it is inspired by 19th-century findings that Polish salt miners had fewer pulmonary problems than other people.
Then, in the 1990s post-communist era, scientists in Poland started to explore the possibility of recreating similar micro?climates above ground, which is when they came up with these salt rock panels, the backlighting and, most importantly, the air?conditioning.www.telegraph.co.uk