TORONTO — The new kid on the international arts festival block is Toronto’s Luminato, which opened for its first crowded weekend on June 1. An expertly programmed kaleidoscope of events, installations, and performances, the festival takes advantage of the city’s best theaters and sites. Eager to be taken seriously, Luminato presented several world premieres by big-brand names, several of which will travel to the New York area. Philip Glass collaborated with Canadian poet Leonard Cohen, and their melancholic “Book of Longing” comes to the Lincoln Center Festival in July. The “Spamalot” team of Eric Idle and John du Prez created “Not the Messiah” — a comic oratorio inspired by “Monty Python’s Life of Brian” — which makes a stop at Caramoor on July 1.

But of all the impressive performances in Luminato’s opening weekend, the most masterful and satisfying one was by a building. The structure is the new expansion of the Royal Ontario Museum, which houses Canada’s most important collection of natural and cultural artifacts. Named the Michael Lee-Chin Crystal, it is a singular sensation. This multifaceted jumble of prismatic forms surges upward toward the street at a steep angle and appears to be gashing into the museum’s surrounding older buildings. Its shiny surface of aluminum cladding is zigzagged with a dynamic composition of narrow and wide glass windows. The building is named for its major donor, Jamaican Chinese billionaire Michael Lee-Chin, who made his fortune in mutual funds.

The “starchitect” responsible for this concoction is Daniel Libeskind, who scribbled his initial design on a napkin five years ago. Its opening was delayed by 18 months; it is the most complicated structure ever built in Canada and a feat of engineering ingenuity at a price tag of $135 million. It coincided with Luminato, which made the building’s opening ceremonies feel like part of the festivities.

Indeed, this new building was celebrated with much hoopla, including a one-and-a-half hour concert on Bloor Street, Toronto’s major thoroughfare, complete with a light show projected on the Crystal’s façade and fireworks. After a private party inside, the building was open all night to the public, who waited in long lines during the day to get their time-slotted tickets.

Though the opening was coincidental to the start of the arts festival, the building has a dramatic performative element. It’s a vivacious dance of interlocking crystal formations creating a new civic space in Toronto’s urbanscape. I met with Mr. Libeskind before the opening to question him about this quality.

“I think a building is a performance,” Mr. Libeskind said. “A building has to perform over a long range of time, to be sustained for many generations. It is a performance that has to be performing all the time and has to show itself to many different people at different times.”

Mr. Libeskind, a former accordion virtuoso, goes even further with his musical metaphors: “The whole harmonic system that informs architecture — proportions, materials, light — is a musical construction. And, for me, architecture is not ‘frozen’ music but a living dynamic experience.”

The new Crystal, which adds 175,000 square feet of new exhibition and public space, predictably rattles some. Mr. Libeskind knows the price of that vertiginous virtuosity — just think of the fate of his similarly clamorous addition to London’s Victoria and Albert Museum, eventually dumped.

It’s not that Toronto is without its interesting architecture; it has Santiago Calatrava’s white-ribbed BCE Place and Will Alsop’s whimsical Sharp Centre for Design, a gigantic checkered box held up by colored pencils. But Bloor Street is a bore architecturally, with its lineup of dull, characterless boxes. The street definitely needed some shaking up.

“There will always be a tension when you do something new,” Mr. Libeskind said. “That’s what part of what architecture is all about: It is something that shouldn’t put you to sleep. And the Crystal doesn’t cut into the older buildings at all. The old structures and new structures are in conversation historically, that’s one of the pleasures of walking through the museum.”

What about the inside? Much criticism has been leveled at flashy buildings that seem inhospitable to the art or objects they’re supposed to house. It’s hard to make this determination just yet in this case, as most of the seven new white galleries are empty. But one of them is earmarked for dinosaurs and another for mammals, sculptural fossils that I think will sit well in the dynamic spaces when they are finally installed next spring. The same goes for the costume and textiles gallery, with its slashing windows.

Only the top-floor gallery is currently outfitted for an exhibit. Hiroshi Sugimoto’s “History of History” is an elegant, if pretentiously titled, exhibition featuring exquisite Japanese objects, masks, and his own photographs of seascapes. The Japanese artist designed a curved wall that divides the space into two sections. It functions as a display case for his photographs on one side and Japanese scrolls on the other. It presented well and shows that Mr. Libeskind’s irregular interiors are workable.

There is a contingent that argues that Mr. Libeskind is copying himself, particularly with his Jewish Museum in Berlin. Though there are some superficial similarities, which have to do with the architect’s personal stamp, the buildings are utterly different in form, feeling, and historical context. One is about tragedy with hope; the Crystal is about celebration. And it’s part of a cultural renaissance happening in Canada’s biggest city. Frank Gehry’s expansion of the Art Gallery of Toronto will open next year. And that energy translated to this project.

Another advantage in this project was that Libeskind did not have to juggle the emotional and political concerns that he faced as master planner of Ground Zero. “That was a difficult project and had all the emotions of tragedy, Mr. Libeskind said. “To bring concensus to that site, to get all the architects, developers, and politicians to work together, I had to make compromises. But I believe in those compromises.”

Though it is rare to hear an architect sound so accepting of changes made to his designs, Mr. Libeskind was sincere. “Ground Zero is going to be a better site and beats the vision I presented in my master plan, absolutely.”

As a master of creating and undertanding symbolic spaces, Mr. Libeskind managed to design structures of great importance in both Toronto and New York. “The Torontonians were bold, and never asked me to calm it down,” Mr. Libeskind said. “They understood that they wanted to assert that the ROM is an important museum and wanted the boldness of that vision to be realized. It will become part of the city fabric, no doubt about it.”