After years of construction, Apple's so-called spaceship campus is nearly complete.

Cupertino on Wednesday announced that the new 175-acre campus, officially dubbed Apple Park, will be ready for employees in April. Moving more than 12,000 employees into the new, ring-shaped building will take more than six months, Apple said.

The 2.8 million-square-foot building is "clad entirely in the world's largest panels of curved glass," the company said. The concept is the brainchild of Steve Jobs, who originally pitched design plans for the campus to Cupertino's City Council in June 2011.

To honor Jobs, who would have turned 62 this Friday, Apple plans to name the theater at Apple Park after him. The Steve Jobs Theater (pictured below) is glass cylinder reminiscent of Apple's flagship retail store on Fifth Avenue in New York City; it's 20-feet tall and has seating for 1,000 people.

The campus also includes a visitor's center with an Apple Store and a café open to the public, a 100,000-square-foot fitness center for employees, and "secure" research and development facilities, Apple said. The surrounding parklands will offer two miles of walking and running paths for employees, along with an orchard, meadow, and pond.

The campus is powered entirely by renewable energy. Apple said the building will have one of the largest on-site solar energy instillations in the world. It's also, according to Apple, one of the world's largest naturally vented buildings, and shouldn't require heating or air conditioning for nine months of the year.

"Steve's vision for Apple stretched far beyond his time with us. He intended Apple Park to be the home of innovation for generations to come," Apple CEO Tim Cook said in a statement. "The workspaces and parklands are designed to inspire our team as well as benefit the environment. We've achieved one of the most energy-efficient buildings in the world and the campus will run entirely on renewable energy."