Apple Inc., the world's most valuable tech company, has submitted to the city of Cupertino, California, revised plans for the Apple Campus 2.

The Apple Campus 2 is a massive ring-shaped office building surrounded by green space. Apple says the new development will provide a "serene and secure environment reflecting Apple's value of innovation, ease of use and beauty."

Under the plan, Apple's existing 2.65 million square feet office buildings will be demolished and replaced by a spaceship-like mega-campus. The circular office building comprises 2.8 million square feet over four stories. Amenities include a café within the main building, a corporate fitness center, and an auditorium seating 1,000 people. There will also be a 300,000 square-feet research facility adjacent to the main building.

The Campus will feature an on-site low carbon Central Plant that will supply majority of the power needed for the campus. Apple also said that the circular roof will be covered in photovoltaic solar panels.

The updated plans show private jogging paths, changes to the fitness center and a new roof made from dark-grey material. The updated plans also include a floor plan for the four-level offices partitioned by symmetrical entrances and a dining area. The proposed corporate fitness center would be expanded to 45,000 square feet from the original 25,000 square feet. The fitness center has lost a floor though, with its height down to 18 feet from the original 30 feet.

The spaceship-like design was unveiled by late Apple co-founder Steve Jobs months in June. Jobs selected a design that was covered in glass, resembling Apple's iconic retail stores. Landscaping around the new mega-campus will include trees, native plants and apricot orchards.

Jobs pitched the design himself to the Cupertino city council. He stated "It's got a gorgeous courtyard in the middle - and a lot more. It's a circle, so it's curved all the way round. This is not the cheapest way to build something." Every pane of glass in the building is curved. The existing ratio of built-up area to landscaping on the site is 80:20, but the new ratio will be 20:80, that is, 80% of the site area will be greenery.

Apple Campus 2 would house 13,000 employees.

Jobs, who succumbed to pancreatic cancer in October, told biographer Walter Isaacson that he wanted to 'leave a signature campus that expresses the values of the company for generations.'

"It's a little like a spaceship landed," Jobs said of the building, which has a circular shape with curved glass all the way around. According to him, Apple has "a shot at building the best office building in the world."

While many have called the project stunning, some critics have voiced against the company's design choices, with the Los Angeles Times architecture critic having called the project a "retrograde cocoon" and with The New Yorker's architecture critic calling it a "gigantic donut".

If Apple receives the requisite approvals, the creator of the iPad and iPhone intends to begin construction next year and open the facility in 2015.

London-based Foster + Partners is the architect for the project. San Francisco, California-based firm ARUP North America Ltd. is the engineer. Philadelphia, Pennsylvania-based The Olin Studio is the landscape architect. Kier & Wright is the planning consultant.

If you want to see more of the Apple campus plans and renderings, you can download 40 MB of PDF files from the Cupertino City Council Web site.