‘The idea,” says Pip Rush, “is to take over the sky.” We’re standing on a 140-tonne crane, 30 metres above the Glastonbury festival site. Rush and his collaborator Bert Cole are sanguine as they take in the view, but I’m clutching the railings, summer breeze blowing through the jasmine of my freaking mind.

From its birth in 1975 until it was rendered obsolete by bigger kit, this crane lifted loads at Avonmouth Docks in Bristol. Rush and Cole bought it for an undisclosed sum, chopped it into two pieces, and trucked them 30 miles to Glastonbury. “It was quite a performance,” laughs Cole. “Police escort and everything. Then we had to put it together again.” He points out all the boltings and weldings, as well as the 10-metre-deep pilings that hold this beautifully incongruous monstrosity in place. Nice, though appreciating the workmanship is hardly a cure for my vertigo.

This crane will form the centrepiece of the Arcadia art collective’s latest installation, Pangea, which premieres this week at Glastonbury and will remain on the site for four years. It is the pair’s response to the question: how do you top a 50-tonne, fire-breathing spider?

The Spider bewitched festival-goers for the best part of a decade. Michael Eavis, who created the festival, remembers being approached by Rush and Cole. “They said, ‘Give us a cheque for £20,000.’ I said, ‘But I don’t know who you are.’ They said, ‘We’ll do a show – and if it falls on its face, you’ll get at least £10,000 back.’ It didn’t go wrong, did it?”

‘Anatomically, it was very incorrect’ … Arcadia’s spider at Glastonbury in 2017. Photograph: Matt Cardy/Getty Images

Originally a tripod, the creature evolved into an arachnid. “Anatomically, it was very incorrect,” says Rush. “Real spiders don’t have built-in fire cannons.” Nor do they have abdomens made from jet engines, legs from Customs scanning machines, claws from log-grabbers, and bodies from helicopter tails. “We wanted to change the festival experience,” says Rush. “Instead of looking at the backs of people’s heads while a band plays, you’re part of the action.”

By 2015, the Spider had evolved into a multimedia spectacular called Metamorphosis, firing flames and laser beams up into the sky. The DJ stood in the abdomen/control booth, which hung above the dancefloor, while acrobats, dancers, performers and puppeteers shimmied up, over and across the creature on tightropes, as Tesla coils generated four-million-volt lightning arcs.

Although it takes four days to set up and four articulated lorries to transport, the Spider has toured to Miami, Bangkok, Seoul, Taipei and Perth. “The Australian trip blew my mind,” says Rush. “The indigenous Australians we met told us their ancestors performed an ancient song about the spider spirit, how its web symbolised community connectedness. They hadn’t performed it since 1901, after a member of the British royal family was rude about it.”

They brought members of the Noongar tribe over to perform this song when the Spider visited London’s Olympic Park last year. “It was a wonderful moment,” says Rush.

‘We’re all in the zone – until Monday morning’ … Bert Cole and Pip Rush with Pangea. Photograph: Sam Frost/The Guardian

From a platform on the Pangea crane, DJs including Carl Cox and Fatboy Slim will play to a 60,000-strong crowd, on a dancefloor ringed by huge speakers. “It’ll be like a giant audio Stonehenge,” Rush says. Flames will shoot from the speakers into the night sky. Isn’t that a health and safety nightmare? “It certainly is,” says Cole. “But we’ve been dealing with the challenge of atomisation for a long time.” Eh? “You’ve got to atomise the fuel before you set fire to it, so that you burn all of it and none of it comes back down afterwards.”

Greasy machinery, millions of volts, flames rising higher than the surrounding hills, a generator running on recycled chip fat, tens of thousands of revellers who perhaps aren’t all sober – are they worried things could go wrong? “We run a tight ship,” says Rush. “People are always amazed when they visit us during the festival. It’s a very sober scene. Not at all what you expect from a rave. We’re all in the zone. Well, until Monday morning.”

'We’re certainly thinking about having performers dangling from the boom'

From 30 metres up, we survey Pangea’s realm. To the south is Dorset, to the north Bristol, and five miles to the west is Glastonbury Tor, surmounting the legendary Arthurian fairy-land of Avalon. “If you climb up that ladder to the top of the crane, you can see the sea,” says Rush. “There’s a really amazing view to the Bristol Channel and Avonmouth.” I look up at the rickety ladder, rising another 20 metres into the sky, and take his word for it.

Pangea, Rush says, is named after “the prehistoric supercontinent where every land on Earth was one and the future had yet to be written. It was a time of possibility.” A blank canvas? “Yeah, that fits with our thinking. We have no idea whether it will work.”

Before we return to Earth, I sit in the driver’s seat of the crane, wondering what sort of carnage I could wreak with the touch of a button. “We got in touch with a guy who was an apprentice when the crane came into service,” says Cole. “He’s been teaching us how to operate it.” Maybe, I suggest, the crane could lift dancers and take them on 360-degree rides. “We’re certainly thinking about having performers dangling from the boom,” says Rush. “We don’t know what it will become over the next few years,” adds Cole. “That’s the thrill.”

• Glastonbury runs until 30 June. Read all of our stories about this year’s festival.