Structural collapse is definitely not the fate you want for your actual theater. But at the Met, that was a distinct possibility. Engineers determined that the set, conceived by Robert Lepage, the Canadian director who is creating this production, would be so heavy — roughly 45 tons — that the floor under the stage might not hold.

So that reality doesn’t imitate art, the Met had a steel company install three 65-foot girders under the stage, a feat of delicate engineering involving thousands of pounds of steel that counts as a permanent structural change to the opera house, the most extensive work yet to prepare for a new production there.

Making such permanent, costly renovations shows the degree to which the Met has bet on the technologically adventurous vision of Mr. Lepage, who has directed stage, Cirque du Soleil and opera productions, including a “Damnation de Faust” by Berlioz that had its premiere at the Met in 2008.

“This is a very challenging creative project,” Peter Gelb, the Met’s general manager, said. “For one of the world’s leading theater directors, it is absolutely appropriate.”

Mr. Gelb declined to discuss the cost of the reinforcement, saying only that it was in the six figures. The company that did the job — Koenig Iron Works of Long Island City, Queens — said its contract amounted to $125,000. That does not include the costs of the engineers and other labor.

Mr. Gelb also declined to discuss the cost of this “Ring,” although he said each installment was at the high end of the amount typically spent for a new production at the Met. With most new productions costing $2 million to $4 million, spending on the cycle could exceed $16 million. The issue is a delicate one at the Met. Mr. Gelb’s ambitious plans have added tens of millions of dollars to the budget of the company, which expects a deficit of from $3 million to $4 million for the season just ended.

Koenig’s president, Barry Leistner, said the reinforcement was tough, performed in cramped spaces and under a tight deadline. The 65-foot I-beams, the sort used to build high-rises, were chopped into smaller pieces, shoved through holes in walls of the rooms below the stage and spliced together. They had to be passed over gas, electric, water and telephone lines that traveled below the ceilings. Each end of the beams was attached to a load-bearing wall.

“We got in and banged it out,” said Mr. Leistner, whose grandfather founded the company in 1907. (Koenig specializes in steelwork for Broadway theaters.) The project began on May 16 and mostly finished last week, with fireproofing starting on Friday. The rooms below — locker rooms for the Met orchestra players, a hallway, the orchestra manager’s office, the conductor’s studio — have to be put back together.

Met officials said the beams, as well as other measures taken to strengthen the stage, would make no difference in how the house operates. “We’ll have a stronger stage as a result,” Mr. Gelb said. “We can add elephants to Zeffirelli productions,” he remarked dryly, referring to the lavish and large-scale stagings created for the Met by the director Franco Zeffirelli, which are being phased out by Mr. Gelb.

Mr. Lepage’s set consists of two 26-foot-tall towers connected by an axis 5 feet in diameter. Twenty-four planks are attached, at their centers, to the axis. The axis moves vertically, powered by a hydraulic system that extends to the basement. The planks revolve individually around the axis. Imagine a series of see-saws placed side by side, that can move independently and collectively levitate.

The system allows for a vast number of possible configurations and will be used to create each scene of Wagner’s epic tale “in a chameleonlike fashion,” Mr. Gelb said. The set will also serve as a backdrop for complex computer-controlled projections, showing the waves of the Rhine, flames around Brünnhilde’s rock or a snowstorm swirling about Hunding’s hut. The system makes for quick scene changes, Mr. Gelb said.

“It’s like the wheel,” he said. “It’s simple and genius.”

Most of the singing will take place on the stage in front of the planks, although characters — and sometimes acrobats representing them — will perform on the structure in its various shapes.

Mr. Lepage used a similar concept for his Cirque du Soleil show “Ka” at the MGM Grand Hotel and Casino in Las Vegas, said John Sellars, the Met’s assistant manager for technical matters. Mr. Sellars said he sent his crew chiefs to study how technicians at “Ka” prepared and tested their set before each performance.

The “Ring” set now sits in a warehouse outside Montreal, near Mr. Lepage’s base in Quebec. By the end of July, it will be in place at the Met and ready for technical rehearsals in August. The cycle’s first installment, “Das Rheingold,” is scheduled for the opening night of the Met season, Sept. 27. “Die Walküre” comes in April; “Siegfried” and “Götterdämmerung” will be introduced in the 2011-12 season; the entire “Ring” cycle will be given near the end of that season.

For the duration of the runs, the set will rest on platforms, or “wagons,” in theater-speak, to the right of the main stage area (from the audience’s perspective). The platforms rest in a well. For performances, they will be rolled into place with the tower-axis-plank complex atop them.

Engineers determined that the concrete slab below the well “was not designed to take those load forces,” Mr. Sellars said. So the beams were placed under the routes to be traveled by the platforms. No major reinforcement was needed for the center stage, visible to the audience, where existing steel beams are sufficient. Also, steel plates were installed on the stage to help bear the towers’ weight as the axis rises up.

Mr. Gelb, after describing the technical issues in an interview, said he wanted to stress something else. “The first and foremost success of any ‘Ring’ cycle is based on the music and the intimate scenes that comprise most of the interaction between the characters,” he said. “This production is meant to be true to the story.”