Located in Oman's southern Dhofar region, bordering Yemen, the valley is the world's largest such reserve, home to around 5,000 frankincense trees that dot the barren earth, their trunks bearing kernels that exude a distinctive woody scent.

"For us, frankincense is more precious than gold. It's a treasure," said Abdullah Jaddad, a frankincense harvester resting in the shade of a tree.

The oil extracted from the sap of the frankincense tree is used in perfume and skincare but it is also sold as solid beads of fragrance in local markets.

The high-end Omani perfume-maker Amouage, which manages the reserve, sells its luxury scents internationally for hundreds of dollars a bottle -- with one limited edition perfume containing frankincense sold for nearly $2,000.

The Dawkah valley is one of the rare places in the world where the Boswellia tree, from which frankincense resin is extracted, grows. Since 2000, it has been a UNESCO World Heritage Site as part of the Land of Frankincense listing, along with Khor Rori, Al Baleed and Shisr.

- Like oil -

With its unique earthy scent, frankincense has long been used as incense, but also in traditional medicine, and even religious rituals.

Before modern technology, the frankincense trade, which began in the third millennium BC, extended from Dhofar via sea and caravan routes to Mesopotamia, the Indus Valley and Ancient Egypt, all the way to Greece, Rome and even China.

"Frankincense had roughly the same value as oil today," according to Ahmed al-Murshidi, who heads the Khor Rori site.

The ancient port of Samahram, which forms part of the Khor Rori site, served as the gateway for frankincense to the world.

As Jaddad collected dried beads of sap from the trees, he told AFP that the type of frankincense found in the valley was the Najdi -- one of four main varieties.

The Najdi and Hojari varieties are used for their medicinal properties, according to Faisal Hussein Bin Askar, whose father founded the Bin Askar frankincense shop, in business since the 1950s.

"The cleaner and purer the frankincense, the more suitable it is for drinking as a treatment, while the rest is used as incense," he said, adding that several factories in Dhofar are specialised in frankincense skincare and oils.

The highest-grade and rarest frankincense has a light green colour.

- 'Quick to anger' -

The resin is harvested by hand using traditional methods that involve cutting the bark to release the sap and leaving it for a few days to harden.

Harvesting the tree requires care and skilled craftsmanship.

As one guide put it to a group of tourists at the Land of Frankincense Museum in Salalah: "the frankincense tree is quick to anger".

"We strike the tree in specific, small spots, about five times, to preserve" the plant, said Musallam bin Saeed Jaddad, who works in the reserve.

"No one should cut open a frankincense tree... it could kill it," he said.

In 2022, Amouage partnered with Omani authorities to develop the Dawkah reserve and provide jobs for the local community, only harvesting a fifth of the trees to preserve them.

Each tree has a unique code and is monitored by a team of specialists, with donations open to anyone wanting to help the reserve in exchange for small gifts of frankincense products every year.

A distillery is set to be built in the reserve to extract the frankincense oil, a process for now completed in France, said Mohammed Faraj Istanbuli, the reserve supervisor.

"The government is carrying out vital projects, like building roads for example, which threatens other areas where frankincense trees grow," he said.

"We bring those trees... to the reserve. We have saved about 600 trees so far."