A new era at Covent Garden began right here. The production of Ariadne Auf Naxos that opened on Friday not only launched the Royal Opera's season but also heralded Antonio Pappano's reign as music director, an arrival that has been eagerly anticipated ever since his appointment was announced more than two years ago.

Unlike his predecessor Bernard Haitink, Pappano promises to be a genuinely hands-on director, with strong ideas on productions as well as musical matters. He has signalled his artistic intentions by inviting German director Christof Loy to the Royal Opera House for the first time, to stage Strauss and Hoffmannstahl's opera about the problems of putting on opera, and clearly Loy and his designer Herbert Murauer have been give a generous production budget. They create their biggest theatrical in the opening moments, when what seems at first sight to be an unremarkable set of an elegant empty salon suddenly begins to rise, revealing another floor beneath where the singers and musicians are preparing for the evening's entertainment.

Such effects don't come cheap, and though the striking visual idea mirrors the structure of the opera itself, in which dramatic conceits nestle within one another like Chinese boxes, it is an extravagance: very little happens on the upper level, for all the machinations of the Prologue are played out below stairs. That action is gently updated to the present day and beautifully observed by Loy and his cast: every characterisation - from Thomas Allen's unkempt Music Master and John Graham Hall's louche, gum-chewing Dancing Master through the seedy retinue surrounding Marlis Petersen's predaciously sensual Zerbinetta to Sophie Koch's utterly serious and passionate Composer - is carefully wrought. The humour is never coarsened and the deep veins of seriousness running through everything are skilfully interwoven both musically and dramatically.

All that is swept away for the opera proper, although it's a sweeping-away that requires a 45-minute interval (far too long). There are few directorial connections between the two parts. Historical periods are elided for Ariadne's encounter with the god Bacchus - her cave is a dressing table, her attendants wear 18th-century costumes, and Zerbinetta is got up as a distinctly down-market tart, determinedly pursued by Nathan Gunn's Harlequin, although Petersen sings her big aria with such elan and touching belief in its sentiments she becomes a far more substantial personality.

Petra Lang's Ariadne (a mezzo soprano fearlessly and very musically taking on a soprano role) and Robert Brubaker's Bacchus sustain their final duet in a way that sheds all the artifice and makes contact with the opera's emotional core. Pappano is at his best here too, conjuring wonderful colours from the ROH orchestra throughout, supporting his singers steadfastly, although his reading takes a little while to settle down and flow naturally.

· Until September 26. Box office: 020-7304 4000. A version of this review appeared in later editions of Saturday's paper