cave in southern Iran's Qeshm island, granting it the widely recognised status of the world's longest salt cave.

Two years ago, Israeli spelunker Yoav Negev decided to complete Frumkin's work, reaching out to Bulgarian cave explorers for reinforcements with the promise of a warm winter adventure.

Negev, founder of the Israel Cave Explorers Club, joined forces with Boaz Langford, a researcher at the university's research centre, to organise a delegation of eight European spelunkers and another 20 locals.

They spent some 10 days mapping the cave in 2018.

A second 10-day expedition this year with 80 local and international spelunkers completed the measuring and mapping of the cave with lasers, determining its length at more than 10 kilometres.

- 'The most beautiful' -

Mount Sodom is essentially a huge salt block covered by athin but resilient layer of cap rock.

The rare desert rains find their way through cracks in the cap rock and dissolve the salt to form small caves that flow down toward the Dead Sea.

Even in the short period of time since Frumkin's mapping, the cave's structure has changed, and will continue to do so.

Much of the cave's interior is covered by a fine dust that blows in from the desert. Massive slabs of salt, some amber-coloured from dust and minerals, jut out in dramatic formations.

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A thin slab appearing to have been sliced out is nicknamed "The Guillotine," while twin slabs in a different hall earned the title of "The Ten Commandments."

Reporters touring the site clambered and crawled through the narrow passages before reaching the "wedding hall," where