As you leave the comparative cool and civilisation of the Ethiopian Highlands, and before you reach the hellish Martian flatness of the salt-pan-and-desert basin of the Danakil Depression, you must pass on your descent a place of sharp, dry mountains, cruel acacia thorn trees and winding, waterless river-beds.

These lawless and trackless valleys of the shadow of death are an endlessly confusing, crumpled terrain and you must stick to the one atrocious track, where travellers would be a sitting duck for ambush. In only one place there did we find water, and, near it, a Tigrean camel-driver with no camels. He and his train had been ambushed the previous year, kidnapped, and marched across the Depression to the low mountains of Eritrea. Without their camels and almost dead from heat and thirst, they eventually wandered back, lucky to be alive.

Now is the season when tens of thousands of camels and their Tigrean drivers will be making their way down for, and back up with, blocks of salt, often travelling at night, and fearful themselves of attack. The camels drink only twice on their journey, walking often at night. There is no fodder down in the Danakil. None at all.

They set out with mountains of straw piled high on their backs, which they deposit at the small villages they pass on the way down. Villagers keep them safe on their roofs for the camels’ return journey. Their drivers bring only dry bread, sugar and tea.

The journey is, by common consent in Ethiopia, one of the toughest trials a man can face.

At its lowest point, 500ft below sea level, is an inferno of a place, one of the hottest and most inhospitable on Earth, where temperatures reach 50C.

A range of volcanoes, some extinct, some still spitting simmering orange lava, lines the basin. A salt lake shimmers and stinks in the burning sun, its centre a dead, black sea, its margins a great, unbroken rim of solid salt crust.

The mysterious lake smells of sulphur when the wind blows across its bubbling vents. And of gas, salt and superheated steam.

With not a blade of grass in sight, and all around a desert of black rocks, the Danakil is a kind of inferno.

One dead bird, turned to leather by the salt, was the only animal or vegetable thing we found in those low hills above the lake. There is not a blade of grass in sight. All the rest is mineral: a dead landscape, alive only with unnatural colour.

How the Afar people manage to live in this place, and why they choose to, puzzles the rest of Ethiopia as much as it does visitors.

Any highwaymen will not be local Afar villagers, who depend upon the traffic of camels and men and look after them. They will almost certainly be wandering bands of bandits-cum-guerillas and will seize adventitiously rather than in any premeditated way, for tourists are very few.

On the Ethiopian side of the Depression there is a strong military presence. Anyone trying to cross the desert and pan would be easy to spot and apprehend, for the only way over is exposed for a day in the white glare and baking sun.

Only the Afar know this weirdly beautiful, desolate place, or move in it with ease. It scares even other Ethiopians. Fierce, volatile and proud, the Afar are a law unto themselves (although they have long abandoned their legendary practice of castrating their enemies and keeping the trophies) but most are not criminals or terrorists. It will be important to try to enlist their help if the tourists are to be found.

Life is cheap here.

Matthew Parris travelled to the Danakil Depression last year

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