The best productions at the Ruhrtriennale festival created a sense of unity with their unique, often vast, settings.For six weeks each year, the Ruhrtriennale festival transforms the economically depressed Ruhr region of northwest of Germany into ground zero for cutting edge art and performance.Since 2002, this lavishly funded event, which puts on roughly 30 productions each summer, has lured artists and audiences to Germany’s rust belt with its robust and unexpected programming. And whereas many of Europe’s summer arts festivals can feel interchangeable, the Ruhrtriennale is devoted to works that can’t be experienced the same way anywhere else. Many have been created specifically for the postindustrial sites that dot the region.Earlier this month, the Ruhrtriennale’s artistic director Barbara Frey inaugurated her third and final festival program with her own staging of “A Midsummer Night’s Dream,” presented in the Kraftzentrale, the cavernous former power station of a disused steel and coal plant. It was the opening salvo in an interdisciplinary program, running through Sept. 23, that includes an immersive production of a Janacek opera and an art installation in a Brutalist church.The desolate set for “A Midsummer Night’s Dream,” designed by Martin Zehetgruber, features rusting cars half-sunken in the earth and sparse trees that suggest Shakespeare’s enchanted forest is on the verge of collapse. This is a gloomy “Midsummer,” both visually (thanks to Rainer Küng’s lighting) and atmospherically, and while it is enlivened by fine acting by a troupe of 10 performers, the production itself is oddly sterile and detached. Dorothee Hartinger’s wry and insouciant Puck and Oliver Nägele’s gruff and bittersweet Bottom are standouts. However, most of the time, the actors, drawn largely from the permanent ensemble at the Burgtheater, in Vienna, recite Shakespeare’s text with fine, crisp diction, but without truly inhabiting their characters.Cast members from “A Midsummer Night’s Dream” from left: Meike Droste, Marie-Luise Stockinger, Sabine Haupt, Markus Scheumann, Sylvie Rohrer, Gunther Eckes, Oliver Nägele and Langston Uibe.Matthias Horn/Ruhrtriennale 2023For a play that dances on the threshold between dream and waking, and art and reality, Frey’s production feels like a slow waltz. (The frequent music box-like tinkering by an onstage musician quickly grew tiring.) There is much to admire, but little to quicken the pulse.I missed the site specificity of the festival’s most memorable productions. When Florentina Holzinger staged “A Divine Comedy” at the Kraftzentrale, in 2021, she made fuller use of the space to create an infernal cabaret-variety show. Although I was not a fan of that production, I must admit that Holzinger’s spectacularly overstuffed staging, featuring joyriding motorcycles and cars, and even a grand piano suspended from the ceiling, was visually stunning. By contrast, Frey’s production, which will transfer to the Burgtheater in September, seems designed for any theater with a rotating stage.There was greater sense of unity between the production and the venue at the world premiere of Gisèle Vienne’s “Extra Life,” at the Salzlager, in the city of Essen.Two years ago Vienne, a distinctive French choreographer and director, was at the Ruhr with her clammy and hallucinatory chamber piece “L’Étang” (“The Pond”). While that previous work was insistently small-scale, with two actors playing 10 roles on a mostly bare set, “Extra Life” embraces the vastness of a former salt storage facility.From left: Theo Livesey, Katia Petrowick and Adele Haenel in “Extra Life,” at the Ruhrtriennale in Essen, Germany.Katrin Ribbe/Ruhrtriennale 2023Like “A Midsummer Night’s Dream,” Vienne’s latest creation is a nocturnal piece. In the vast, often fog-shrouded confines of the Salzlager, she unspools a simple yet enigmatic tale about two estranged siblings (Adèle Haenel and Theo Livesey), who reunite at a party and rekindle their relationship, sifting through a painful family history. A third character (Katia Petrowick), who emerges during their long night of the soul, might be a kindred spirit who follows them from the party into the woods. Or perhaps she is a composite of figures from the siblings’ past, or of unconscious wishes.This is a demanding and elliptical production, in which much is implied, but little is ever settled. Vienne and her fellow artists achieve uncanny and cathartic effects through pared-down dialogue, controlled slow-motion choreography and dazzling laser stage lighting (by Yves Godin) that suggests both being at a club and inside a video game. Immersed in the swirl of fog, lasers and a synthesizer score by Caterina Barbieri, the audience seems bathed in postindustrial electricity.With its disquieting blend of surreal and blandly quotidian elements, “Extra Life” can be an exasperating puzzle. It’s best to just surrender to its visual and sonic rhythms over the course of its unhurried 140 minutes. Over the coming months, the production will travel to Germany, Belgium, Switzerland and France.This is Frey’s last summer leading the Ruhrtriennale. Her time at the festival has widely been judged a success, especially next to the troubled reign of her predecessor, Stefanie Carp. But the creators Frey championed were often extreme, or obscure.From next year, the Belgian director Ivo van Hove will be in charge. Like his predecessors, he is sure to put his stamp on the festival, and there is no doubting that van Hove has a questing and disruptive bent. The Ruhrtriennale will give him his biggest canvas yet. I’m curious to see how he chooses to fill the Ruhr region’s majestic cathedrals of industry.RuhrtriennaleThrough Sept. 23 at various venues in northwestern Germany; ruhrtrienniale.de. More