If you're someone who has been following the construction progress on Apple's new $5 billion "spaceship" campus in Cupertino, California, you've likely spied the towering pyramid of earth looming directly behind the massive circular structure.

Unlike other construction projects that might haul this clean fill away, Apple has big plans for the valuable soil. According to CEO Tim Cook, the massive pyramid will slowly be distributed around the 175-acre campus to help nourish a forest of more than 7,000 trees.

"Hard to know which is more beautiful, the building or that pile of dirt," Cook recently told Vogue during a tour of the site.

When the late Steve Jobs first commissioned the design for the campus in 2009, he was adamant about making green space a priority. To that end, roughly 80 percent of the campus will feature open, natural spaces. Before demolishing the old Hewlett-Packard site, Apple also dug up and preserved more than 1,000 mature trees for re-planting.

AppleA before and after of Apple's new 175-acre campus. About 80 percent of the property will be left natural and open. (Photo: Apple)

"It's pretty ambitious," Dave Muffly, a full-time arborist hired by Apple to head its tree landscaping, told the LA Times. "Some of these development projects, they don't see the value of transplanting these larger trees. They only see the dollars and say, 'Oh my goodness, it’s so expensive.' But some people recognize that if you bring in old trees, that as soon as my project opens, I'm going to have a landscape that is already pretty established."

Trees slated for the new campus include oak trees, plums, cherries, persimmons, and yes, apples. At last count, 243 apple trees will be featured inside the courtyard of the new Apple HQ. Golden Delicious, Jonagold, Pink Lady, Sierra Beauty and seven other varieties will be available to the more 14,000 employees expected to work there.

In addition to the natural beauty of the campus, Apple is also working to make the campus one of the most sustainable in the world. About 90 percent of the materials from the demolished Hewlett-Packard buildings will be used in its construction, including the recycling of old cement. Instead of being mulched or tossed, trees not slated to be re-planted were sent to a lumber mill. Energy to power the site, including the 770,000-square foot circular building, will come from on-site, 100-percent renewable sources.

“We have a shot,” Steve Jobs said in 2011, “at building the best office building in the world."

Apple's new campus is expected to open early next year.