Apple CEO Tim Cook has officially opened the auditorium and events venue at the company's Foster + Partners-designed campus, where today's Apple Event took place.

Named after Apple's late founder, the Steve Jobs Theater held its first event today, during which the tech giant unveiled a variety of products including the rumoured iPhone X.

The venue was designed by UK firm Foster + Partners as part of the vast Apple Park, which contrary to Cook's comments, the company has been slowly moving in to since April 2017.

"We'll start moving into Apple Park later this year," said Cook during the Apple Event, on 12 September 2017. "The first big step is the opening of the Steve Jobs Theater."

Those attending today's event shared images and videos of the theatre on Instagram. Largely underground, the 1,000-seat auditorium is topped with an circular pavilion that features 20-foot-tall (six-metre) glass walls and a thin disk-shaped roof.

It sits on top of a hill among the 175 acres (71 hectares) of landscaped grounds, which Cook said "was converted from a sea of asphalt".

"Apple Park is designed to be seamless with nature," said Cook, who took over as CEO after Jobs died in 2011. "It's open, its transparent and it brings the outside in."

"Steve's vision and passion live on here at Apple Park," he added. "His vision for Apple Park was to create an incredible workplace of the future."

Most of the 12,000 employees on-site will be housed in a huge ring-shaped building, also designed by Foster + Partners, along with the majority of structures on the campus.

"Apple Park has been built to reflect Apple's values, for both technology and the environment," Cook said. "It's powered by 100 per cent renewable energy. We have one of the world's largest solar installations right here."

Reactions to Apple Park, which was captured in drone footage by Duncan Sinfield last week, have so far been varied. Wired magazine's review concluded that the campus "sucks", while the company's chief design officer Jonathan Ive described it as "nice".

Reports suggest that some of the employees who have already moved in agree with Wired, as they dislike the open-plan office spaces enough to consider quitting.