My Borneo jungle adventure begins in civilised Kuala Lumpur. It’s late and I am sipping a negroni at the bar in No Black Tie, a state-of-the-art jazz club crowded with excited musicians, the talk all about the upcoming Borneo Jazz Festival. “Each year, we bring everyone together in the tiny town of Miri, just on the border with Brunei,” says Evelyn Hii, the club’s owner, who organises the festival in her native Sarawak, one of the two Malaysian states on the island of Borneo. “Jazz artists from across the world will perform at night, conduct masterclasses during the day and discover the magic of Miri.” The prospect of a trip to Sarawak, the land of white rajahs and headhunting tribes , fills me with excitement. So a couple of days later, I book a long weekend of non-stop jazz and a flight to the Unesco World Heritage-listed Mulu Caves – Miri is a stepping-off point for exploring some of the largest caverns on Earth, in the depths of Sarawak’s ancient equatorial rainforest. After dumping my bags at my hotel, I arrive at the Coco Cabana just before the sunset inauguration ceremony kicks off the festival. The venue, a soaring wooden auditorium, dominates a narrow palm-fringed headland jutting into the sea. At its tip stands the Seahorse Lighthouse, around which dancers, musicians and a mystical storyteller from the Kenyah tribe, resplendent in traditional hornbill feathers and embroidered beads, bewitch the crowd with a sacred welcome ritual. The ceremony is “like a mix between jazz, hip hop and music from the rainforest – amazing!” says American pianist Kirk Lightsey, one of the stars of the festival. “The storyteller is like a rapper, with his grandparents as backing singers and musicians playing traditional sape guitar and gamelan-style xylophone – totally modern and totally traditional at the same time,” the sprightly 82-year-old tells me. “I came here expecting to be surprised and I am not disappointed – I mean, jazz in the jungles of Borneo!” The Coco Cabana’s two-storey dance hall is already packed by the time the first musicians arrive on stage; an old-time big band fronted by Shanghainese star Jasmine Chen, whose songs feature in the 2018 movie Crazy Rich Asians . As the evening unfolds, the audience is blown away by the electrifying jazz rock of Tokyo’s Fox Capture Plan and romanced by the cool Blue Note music of Lightsey’s trio, who accompany the seductive scat and soul of Chicago diva Chanda Rule. Suddenly, everyone is dancing to the salsa and merengue rhythms of Mexican combo Ireson. Midnight comes and goes, crowds form around pop-up bars mixing cocktails based on tuak , Sarawak’s lethal fermented rice wine. Food stalls cook up weird and wonderful jungle dishes such as foraged midin and paku vegetables wok-fried with balacan paste, succulent roast wild boar and tender bamboo-steamed chicken. The party carries on into the early hours around the outdoor Seahorse stage, with jam sessions and rare grooves mixed by DJ Maestro, who has come all the way from Amsterdam. The next day, serious music fans head back to the Coco Cabana for the masterclass workshops while I discover Miri. It was transformed from a sleepy fishing village into a boomtown just over a century ago, when Shell drilled its first oil well here. Miri still has the feel of a rowdy cowboy town, even though the petroleum and gas industry is not what it used to be, the boats heading out from town to offshore rigs no longer full of free-spending contract workers from the West. Nevertheless, half the city centre seems to consist of bars, clubs and karaoke lounges, all apparently packed at weekends, when Miri is invaded by visitors from neighbouring Brunei looking for fun. There is little here for sightseers, though, apart from the Tua Pek Kong Chinese temple, which is decorated with a striking series of mythological Buddhist murals. Next to the temple is a bustling fish market, where fishermen moor their boats each morning and unload their wriggling catch – giant stingrays, baby sharks, plump lobsters. In the covered Central Market, wizened women bent over bubbling pots prepare local specialities such as kolo mee dried noddles, tangy Sarawak laksa and, for the adventurous, pig’s stomach cooked in pineapple and pig’s blood. Tamu Muhibbah, the sprawling tribal market, is a cornucopia of unique products: fragrant Bario rice and salt from the Kelabit highlands, juicy jungle mango and durian, tuak made in native longhouses and rare bird nests. The parade of international jazz bands delights the enthusiastic public over the weekend, but a surprise has been saved for the finale. The stage welcomes stars of the local music scene, hip hop artists Arabyrd and Benzooloo, from Sarawak and Sabah, respectively, who strut their stuff before Brunei rapper Zed Peace closes the festival. The audience goes wild; kids start breakdancing, and many want a selfie with their idols. Looking on are several of the established jazz musicians. Rule tells me, “I have never played at a festival where we get to hang out with both other performers and the locals, and I mean, just look at how supportive and enthusiastic the audience is!” After a 30-minute flight , we touch down at tiny Gunung Mulu National Park airfield. An almost 300km-long labyrinth of caverns lies beneath this jungle and four of these immense caves can be visited in two memorable days. Numbers are strictly limited to 250 visitors a day, always accompanied by tribal guides, so there are none of the problems of overtourism that threaten other ecosystems. Visitors on a budget can bypass the Mulu Marriott Resort and put up in cheap and cheerful homestays around the park headquarters. As we stride along a raised boardwalk that runs for 5km through dense tropical vegetation, my Iban guide, Larry Siga, points out exotic birds and butterflies, creepy centipedes, orchids and pitcher plants. He takes me through Deer Cave, the world’s largest cave passage and home to 3 million bats, and the smaller Lang Cave, which resembles a fantasy cathedral, with thousands of stalagmites and stalactites. The next morning we set off from the jetty below the Mulu Marriott in a dugout canoe powered by a powerful outboard motor along the winding Melinau River to explore other caves. A steep staircase cut into the rock face climbs through the undergrowth to Wind Cave, which is true to its name, gusty breezes whistling through a series of narrow, otherworldly caverns. Another intimidating climb leads to Clearwater Cave, its entrance strewn with black boulders covered in moss, leaves and lichen that glow fluorescent green in the sunlight. We explore a mere fraction of the cave complex’s 220km of subterranean passages, before heading back down to where our boat is moored, along with those of other cave visitors. An underground river from Clearwater gushes out into a lake nearby and when we get back down to it, we leap in for a well-earned swim. This year’s Borneo Jazz Festival will take place from July 17 to 19 as part of a month of festivals in Sarawak titled “Lets Get Tribal”.