Irish band U2 have christened the stage of the new $US2.2 billion ($3.4 billion) spherical stage structure dubbed the "future of music" in Las Vegas, Nevada. 

The world's largest spherical structure's 111 metre-high exterior is covered entirely by fully programmable LEDs. 

Inside, it is an immersive experience with the world's largest and highest-definition wrap-around LED screen. 

It can seat 17,500 people, and the venue is equipped with thousands of speakers claimed to deliver a "crystal-clear", multi-layered experience.

U2 became the first band to perform at the new venue when they played there on Friday night.

The group are playing 25 concerts at the Sphere in a run lasting until December 16.

"It's probably the most beautiful thing I've ever seen in my entire life," said Paxton George, an 18-year-old from San Diego who watched U2 with his father.

"I'm not even joking. Especially the last couple of songs with a sunrise and then just pure daylight. It was so weird and it was amazing.

Lisa Fitzpatrick, a fan from Dublin said: "It was just a wonderful experience. U2 are just the greatest band of all time."

The opening attracted many celebrities including actors Byran Cranston, Aaron Paul, Dakota Fanning and Josh Duhamel. 

Humble beginnings

The structure began as just a sketch of a circle with a stick person inside, drawn by James Dolan, the executive chair of Madison Square Garden and owner of the New York Knicks and Rangers.

He and MSG Ventures CEO David Dibble were trying to create a plan to give the entertainment venue industry a "face lift" in Las Vegas.

Both experimented with different shapes for the structure — such as a muffin, a box and even a pyramid — until Mr Dolan drew the circle and stick person on a notebook.

"It really is a new medium," said Dolan, speaking to the media during a walk-through on Thursday.

"When you're in the Sphere, you don't get told what to look at. The audience decides what they want to focus on."

AP