Nakhchivanis, natives of Azerbaijan's autonomous exclave, claim to be internationally recognized for three things: salt, girls, and melons – in that exact order. Their salt, which they harvest from local caves, is not just special in taste, they say, but also because of its unique restorative properties. Locals eat it to avoid arthritis and retreat into the kitted-out caverns for days at a time to treat asthma and other respiratory illnesses.

The most illustrious and well appointed of these caves is Duzdag, burrowed into a peak a 15-minute drive outside of Nakhchivan City. A 300-meter long tunnel so salt-rich that it's all but crumbles when touched, Duzdag is famous largely due to the legends associated with it and for the ease of access created by its horizontal structure. Also, it is stunningly well-appointed: Bare halls have been adorned with marble latticework and wooden lodges have been built into the salt walls. All of the rooms – there are around 300 beds available – in the tunnel's nine galleries are equipped with hotel amenities, and the broader complex includes recreational facilities. As a bonus, the entire treatment is bespoke for each patron. Most people come to stay for five- to six-day stretches at a time, but 200 or so daily patients also pass through for therapies and visitations that are specially arranged by on-site doctors.

The prehistoric context, in combination with the creature comforts Duzdag offers, creates a bizarre but welcoming atmosphere unavailable anywhere else on Earth. Wandering through caves filled with lovely huts and true believers is less alienating than it is a shock to the system. This place seems more like a 'Star Trek' set than a retreat, but then the maid arrives. Even more shockingly, the treatments are relatively affordable, running between $40 and $55 per day for a room. And the surrounding mountains of Nakhchivan, replete with panoramic views of the Aras River and Iran beyond, are worth a look for their stunning beauty.

It's easy to doubt Nakhchivanis' belief in the healing power of the caves and the land around them – prepare to be told that men recover from cancer by eating local grasses and that Noah founded the regional capital. But the republic's mere existence is almost equally implausible. The roughly 2,000-square-mile swath of mountains is sandwiched between Armenia, which blockaded it to devastating effect in the 1990s, and Iran, a country not commonly associated with restraint. The land may not have special powers, but there is definitely something singular going on both above and below ground.

More information: The easiest way to reach Duzdag is to drive from Tblisi, Georgia – an underrated city in its own right. Underground rooms run from $40 a night and are located a short way from the main hotel.