With a terrific "Tristan und Isolde" and a peculiar "Parsifal," the Bayreuth Festival has rolled out its full repertory for the summer ¡ª a marathon of seven operas in a span of nine days.

There are many things to admire, a few to deplore, and two achievements that tower above everything else: Christian Thielemann's inspired conducting of the four-part "Ring" cycle and a superb performance by Swedish soprano Nina Stemme as Isolde.

"Tristan," seen Tuesday night, is the biggest success of the season in matching high vocal standards to intelligent staging. Director Christoph Marthaler effectively transposes the tale of the doomed lovers in a 1950s Europe of austerity and alienation, using little scenery beyond fluorescent lights, some chairs and a hospital bed for the dying Tristan.

Isolde is one of the most daunting roles in opera, yet Stemme tears into it with seeming ease and abandon, her large voice warm and well-focused right up to high C. It helps that she and the fine American tenor Robert Dean Smith as Tristan, both repeating their roles from last year, look the part of lovers who could be instantly attracted to one other.

"Parsifal," performed on Wednesday night, is a mirror image ¡ª a dubious production concept in the hands of a less-than-stellar cast.

Wagner's last opera, about the Holy Grail, has long been considered something of a religious experience at the Festspielhaus. But not to Christoph Schlingensief, whose 2004 production (still being performed at the current festival) takes a breezily iconoclastic approach. Making use of an incessantly revolving set, falling and rising scrims, and projections of videos and still photos, he bewilders the audience with a frenetic multicultural experience that includes African tribesmen, Arab women, a midget ¡ª and a dead rabbit.

The images can be provocative and even beautiful, but more often distracting and, in one case, downright nauseating: As some of Wagner's most ethereal music plays at the opera's end, we watch a film of the rabbit's carcass being devoured by maggots.

Neither Alfons Eberz as Parsifal, Evelyn Herlitzius as Kundry nor the other soloists had the kind of voices to take one's mind off such nonsense.

Compared to "Parsifal," Tankred Dorst's new production of the "Ring" is only a modest failure.

It has moments of great ingenuity, but his concept that "the gods are among us but we don't see them" hasn't been developed sufficiently ¡ª and too often he leaves the singers to fend for themselves. What distinguishes this "Ring" is Thielemann's interpretation of the score, which unfolds with grandeur and a sense of inevitability at his hands.

That leaves "Der Fliegende Hollaender" ("The Flying Dutchman"), seen on opening night in a revival of a clever production by Claus Guth that turns the story into a psycho-sexual nightmare. Only a weak cast keeps it from being a complete success.

There will be two more complete "Ring" cycles, and the three other operas will be performed in rotation before the festival ends Aug. 28.

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Three repertory staples are absent this season: "Lohengrin," "Tannhaeuser," and "Die Meistersinger von Nuremberg." The latter returns in 2007 in a new production, the first at Bayreuth by Katharina Wagner, who is rumored to be the favorite to take over the festival from her 86-year-old father, Wolfgang.

Wagner also wrote three early operas that are deemed unworthy to perform at Bayreuth: "Die Feen," "Das Liebesverbot" and "Rienzi." They are, however, represented in the CD kiosk to the left of the opera house. There, too, one can find recordings of long-forgotten operas composed by Wagner's son, Siegfried, titles such as "Der Baerenhaeuter" ("The Man in a Bear's Skin") and "Schwarzschwanenreic h" ("The Kingdom of the Black Swan.")

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Taxis are plentiful and there are parking lots nearby, but the best way to get to the Festspielhaus is on foot. It takes about 30 minutes from the center of town. Walking north past the train station you cross Walkuerenstrasse, Meistersingerstrasse and other streets named for Wagner operas until suddenly you glimpse the imposing brick and sandstone building atop the so-called Green Hill. If you time it right, you approach up a garden path just as a group of horn players appear on the balcony in front to signal that the curtain is going up in 15 minutes. They do that by playing a theme from the act about to be performed. With 10 minutes to go, they play the theme twice, then three times when there's just five minutes to get to your seat.

It was from a window near this balcony that Adolf Hitler, a regular at Bayreuth, waved to the audience during intermissions. Slightly down the hill is a plaque commemorating two festival soloists who were murdered in Nazi concentration camps in 1943 ¡ª Ottilie Metzger and Henriette Gottlieb.

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One singer won an ovation at Bayreuth this season without appearing on stage ¡ª Placido Domingo, spotted in a center box during the first performance of "Die Walkuere." As the audience was settling into their seats following the second intermission, a man pointed to the box and cried "Bravo, Domingo," triggering a sea of turning heads and much applause. The tenor stood up, smiled and waved appreciatively. Perhaps he was there to hear the evening's Bruennhilde, Linda Watson, who will sing the role next spring for the Washington National Opera, a company Domingo runs. He will appear with her as Siegmund, a role he has sung at Bayreuth.