The last time I visited an NVA art project - the epic light-and-sound installation The Storr: Unfolding Landscape, on Skye - the mist was so thick, the rain so torrential, that my main aim was not to break my neck on the way down. Two years on, arriving in remote Kilmartin for NVA's new project, Half Life, I find myself in similar deluge.

Half Life is a sound-and-art installation that aims to "reveal the dark but inspiring mindset of Scotland's Neolithic inhabitants." While the Glasgow-based environmental art charity NVA is reluctant to give out specific details, the result will involve soundscapes culled from the natural world (designer Toshiyo Tsunoda apparently stood for five hours with a contact microphone on a fence, in one instance), installations created from it (an upturned tree inserted into a millwheel) and a devised theatre event in the evening, created with the National Theatre of Scotland, around a newly created tree-trunk henge.

NVA has a penchant for working in epic landscapes so remote they require serious effort to get there. "It's part of the thrill, both for us and the audience, I think," says NVA's project manager, Jon Clark. Set up in 1992 by creative director Angus Farquhar, NVA produces site-specific events and interventions which have ranged from the permanent, such as the Hidden Gardens in Glasgow, to the transitory, such as The Storr or the Glasgow Light Festival, Radiance 05.

Kilmartin is different again, not least in its collaboration with the National Theatre. This remote corner of Argyll is one of Scotland's richest prehistoric landscapes, with the highest density of cup and ring marked rocks (deep carvings of concentric circles whose meaning is still a matter of debate) in the British Isles. Later archaeology includes Dunadd, a settlement topped by a stone with an imprint of a footprint. It is believed that the kings of Scotland were once crowned here. The views stretch from the Paps of Jura to the Corryvreckan whirlpool.

Farquhar and I drive around the glen in an area of flat, beautiful, fertile-looking land pocked with rocky outcrops and piles of stones. Cairns and burial mounds tramp down the valley floor, as if some passing Neolithic giant has left raised rocky footprints. This is a landscape of the dead. If the living were here, they trod more lightly.

"No settlement has been found, and we think this would have been a vast sacred area intended for burial," says Farquhar. Some have suggested the cup and ring marks denote the entrances to this sacred landscape.

"There was certainly a huge ritual element that didn't change over a few thousand years. People would leave the dead out to be picked clean by birds and animals. Then the bones would be dismantled, heads removed and elements put in burial chambers. This process could take years, at the end of which, finally, the bones might be reassembled before finally being perceived to have moved on."

It is the idea of these ancient practices, and their demise, that has inspired Half Life - a term which, as those with memories of school chemistry will recall, relates to the time it takes half the quantity of a radioactive (or biological) substance to decay.

"It seemed an appropriate name for this project, in terms of how long it takes something to die away," explains Farquhar. "How long does it take for a memory to fade, for example? There's a sense of it as a poetic description of a form of purgatory, something between life and death which touches upon the possibility of a dislocated place before souls are finally laid to rest. So in that way, the idea of Half Life is very much a reflection of Neolithic burial practice."

By day, armed with a map and rather personal field "notes" from a certain Professor Jacob Wheeler ("It's drawn from real material," says Farquhar obscurely, "but for particular reasons we don't want to give away the archaeological inspiration. Argyll is a small place") visitors are encouraged to visit some of 16 earmarked archaeological sites (of a massive 350 in the area) picked out by NVA with local archaeologist and curator at Kilmartin Museum, Dr Sharon Webb.

By night, in a newly-made clearing at a Forestry Commission site near Achnabreck, which includes a new permanent auditorium for the people of mid-Argyll, there is a devised theatre production written by novelist Thomas Legendre and directed by Mark Murphy, pitting the archaeological against the spiritual to a soundtrack by composers Rhodri and Angharad Davies.

The installations range from starkly stripped Forestry Commission pine trees - giving a powerful sense of the force, both of nature, and of man's relationship with it - to sound interventions around cup and ring marked sites. They've been visually designed by Simon Costin alongside architect/engineer James Johnson and sonically curated by Barry Esson.

Costin is an NVA veteran, having been involved with two previous projects, interspersed with his other life as a set designer of fashion shows. Next week he will be at New York Fashion Week. He says: "Hopefully this will bring a different perspective to the way people view the landscape. I hope what we're doing will inspire people to use their imagination."

The aim is to enhance the experience of the historic landscape. The danger is in creating a romanticised experience. "We have to be clear about this. What we're doing is art, not historical interpretation," says Farquhar. "What's interesting for me is that this is the point when human consciousness was evolving fast, where we first decided to make marks on a rock; where we thought it was actually worth the time to do this."

But the connection of us all to this "lost" past is perhaps clearer than we think. Farquhar is staying in a house which, by serendipity, is close to one where his grandfather lived. Farquhar took his two young daughters to a burial cairn a few hundred metres from the house - a mound of stones with a slab of rock over the top, the chamber empty. "My five-year-old asked me where the bones had gone. I lowered her into the hole and she said, It's a miracle!'", Farquhar laughs. One senses it's this sense of wonder that he wants to instil in all visitors to Half Life .

  • Half Life is at Kilmartin Glen, Argyll, September 4 to 16.