Las Vegas has a tendency to overwhelm. There’s an unending stream of spectacle awaiting us all on the Strip, dozens of entertainment experiences that stun and amaze, then we move on to the next one on our next visit. Because once you’ve checklisted the experience, it’s time to find out what else is out there.

“O” is the exception. It can never be mastered, only appreciated. When the Bellagio teamed with Cirque du Soleil 19 years ago to craft an aquatic dreamscape and a story that elegantly plays with the concept of infinity, the creative artists behind the show perfected the formula. “O” is beyond cinematic, offers just the right amounts of humor, romance and surrealism, and never ceases to surprise no matter how many times you’ve seen it. There are always more discoveries to be made in the “O” Theater.

Written and directed by Franco Dragone and witnessed by more than 15 million showgoers, “O” is nothing short of a Las Vegas institution, as essential to the Strip’s storied entertainment history as any legendary headliner ever has been. An international cast of 77 acrobats, synchronized swimmers, divers and characters fly and splash their way above, around and within the true star of this one-of-a-kind production: the 1.5 million-gallon pool that may be the most magical stage on the Strip.

It’s difficult to single out memorable highlights or applause-inducing moments in “O,” because that would be every act. The passionate performance of characters like the curious Philemon, the audience’s guide on this adventure, or the enchanting Le Travesti is just as striking as the cadre of “zebras” dangling from a swaying jungle gym-like suspension. The can-you-believe-that-just-happened factor is just as strong with L’Allumé (the “man on fire”) as it is with the heart-stopping Bateau, a steel-framed airship in constant motion decorated with 11 acrobats flying all around it.

Only a show with this much action and artistry could feel fresh after such a long run. But that doesn’t mean there haven’t been small changes to “O” over its lifetime. “You always have to respect the concept,” explains artistic director Ria Martens, a veteran of the Cirque du Soleil team. “That’s the base, so it’s our job to continue to go in that direction. The changes I make are when the artist is ready to be pushed, whether it’s part of the character or acrobatically or otherwise. You’ll see it in the energy they have, that’s the change. It’s subtle.”

There’s nothing subtle about the audience reaction to “O,” which very quickly pulls viewers into its own fantastic world where things can be astonishing, silly, sexy and creepy at the same time, and it’s all awash in freedom, thanks to the one-of-a-kind theater that allows its performers to do the impossible whether they’re moving through water or air, unrestricted and unlimited. How could you ever get enough?

Bellagio , 7 & 9:30 p.m. Wed.-Sun., $98.50-$155 plus tax and fee. 702.693.8866