Music: DALHALLA Sweden

Midsummer in mid-Sweden, and the weather is supposed to be warm, the skies clear. But the gods did not smile last Wednesday. For former opera singer, Margareta Dellafors, the disruptive tempest must have seemed like a fatal blow to her ambitions to transform a vast, disused limestone quarry that she discovered in 1991 into a summer music venue.

She need not have worried too much. For an hour the excellent Royal Stockholm Philharmonic and four magnificent singers under Okku Kamu's direction bravely battled with cold, wind and rain before being forced to abandon a concert designed as a taster for more ambitious things to come.

Soaked and shivering in our orange plastic ponchos, we had nevertheless seen and heard enough to be convinced that Dalhalla - as Dellafors has wittily re-christened the former Draggangarna - has an immensely promising future. If all goes well, there will be a concise Ring next year, and an annual summer festival thereafter. Co-operation with Savonlinna and other opera companies is at planning stage, and Dellafors clearly has a persuasive way with funding bodies and generous individuals. By 1996, a roof of some kind should be in place to offer protection from inclement weather, if not from the low temperature, which was what finally did for last week's concert.

First among Dalhalla's many virtues is its quiet location, close to the small town of Rattvik and the beautiful Lake Siljan. Then there is the sheer sight of it. You approach down a long, narrow lane that takes you deeper and deeper into the forest. Suddenly a twist in the lane and there it is, an almost sheer-sided rectangular arena a quarter of a mile long, 175 metres wide and 60 metres deep. A natural stone platform juts out into the flooded bottom of the pit. How can mere humans fill such a great void with sound and without amplification?

But as soon as Kamu had disembarked from the rowing boat that had brought him to the platform and launched into the overture to Wagner's Die Meistersinger, it was plain that there was no difficulty. Partly because the water acts as an acoustic reflector, the sound strikes the 2,500 souls seated across the pond with a surprising immediacy. The balance is miraculous too, and the acoustic has a lovely warmth and a languishing distant echo that adds mystic aura, perfect for Wagner. The Fidelio quartet confirmed that voices carry as well as instruments. But it was a spotlit lone trumpeter, sounding his distant fanfare in Beethoven's Leonora No 3 from a high stone gallery, who provided perhaps the evening's most powerful drama. The chill in the spine at this moment was not of the elements' making.