NVA's Speed of Light, Arthur's Seat, Holyrood Park, Edinburgh

Much more than a walk with a torch, but perhaps a bit less than the spectacular promised or hoped for.

Experienced on the final dress rehearsal, with less human pixels than will be the norm, it would be unfair to judge  The Speed of Light , a joint Edinburgh International Festival and Cultural Olympiad commission, conclusively.

But one suspects that even twice as many runners will struggle to compete with the municipal lightshow of Edinburgh behind, or fill the darkness as dazzlingly as must have been intended on paper. An event in which the audience are both spectators and raw material, NVA’s latest piece sends walkers up Arthur’s Seat in darkness, their way lit by lightsaber-style staffs and the glitter of choreographed runners in light-suits, making patterns against the blackness.

On a fine night, with a ruddy moon over the Firth of Forth and the deep ocean phosphorescence of the runners pulsing below there’s enough strangeness and beauty to make it memorable.

But what really cuts through is the eccentricity; the pilgrim solemnity of walkers creating a chain of lights up the hill, and the odd intersection of health and safety advisories and the eerie singing of the electronic staffs, which respond to altitude. It may not quite reach the peak it intended, but there’s nothing else in the Festival quite like it.

To 1 September (0131 473 2000)