Ariadne auf Naxos, New Theatre, Cardiff

How do you cap an evening of pure magic? With more magic. Perhaps a quick coup de théâtre.

How do you cap an evening of pure magic? With more magic. Perhaps a quick coup de théâtre. A Greek trireme that descends from the flies. A love duet to end all love duets. But then, if you're Hugo von Hofmannsthal, let alone Richard Strauss, rapture and enchantment are grist to the mill.

Welsh National Opera's new staging of Ariadne auf Naxos - just a waft of the designer Dale Ferguson's sea-green mollusced beach, into which Janice Watson's Ariadne fuses like a moribund chrysalis - puts you in receptive mood. The orchestra plays its heart out for WNO's saviour, Carlo Rizzi, who has bailed out the company after the young Russian conductor Tugan Sokhiev jumped ship.

It's the arrival of Peter Hoare's Bacchus that ices this sumptuous Welsh cake. What a shiveringly beautiful sound this tenor makes; Ariadne's rescue by Zeus's golden boy, the two circling each other in a wary courtship of pent-up passion, was as entrancing as if Siegfried Jerusalem had jetted in. That visual coup was stunning, too: Dionysus's boat descending slowly from the skies. "Bin ich ein Gott", he sings, pinching himself to make sure. The ending is as fabulous as that of Rosenkavalier - especially when the director, Neil Armfield, feeds on first Katarzyna Dondalska's Zerbinetta ("When the new God appears, we surrender, struck dumb") and then Alice Coote's Composer. You could feel the tears welling.

WNO is itself a noble trireme: the ship that sails on, delivering quality even when London's opera looked rocky. Despite its present problems, this memorable Ariadne is no surprise after its Queen of Spades and Pelléas. When Cardiff opens its opera house next year, it will embrace a world-class company.

WNO serves up casts to match. Watson's Ariadne easily outbid Covent Garden's Anne Schwanewilms - at her peak among German sopranos. Her moves melted as she shifted, cocooned like a part-petrified Niobe. Unlike Dondalska's oboe-led Zerbinetta, who seemed underpowered except in her uplifting top range, Watson fills the auditorium even from rear-stage. "What remains of me in your arms? What becomes of me as I cease to exist?" We know: her obbligato bassoon has told us. Ferguson's creeping firmament, all pinprick lights, was captivating.

Coote's fretful Composer is a fabulous find: her tone, strength and personality are entrancing; her range and variety should get better still. D'Arcy Bleiker's Harlequin and an inventive basso Truffaldino from Tim Mirfin all confirmed that Armfield had focused on the funnies. Brian Galliford's Dancing Master and Richard van Allan's hilarious Hitler-ish Major Domo outburst were among the delights of the cheerfully cramped "below stairs" Prologue.

To 25 September (029-2087 8889), then touring to 7 December ( www.wno.org.uk)