DETROIT – Outside General Motors' new world headquarters, between the 12-story building and the city's first new skyscraper in more than 30 years, sit two red Chevrolet pickup trucks.

One is a 1963 Chevrolet K20. The other is a new Silverado EV. The trucks, while part of a temporary holiday display, are symbolic of what's inside the new global offices for the Detroit automaker: its past and present, woven together.

GM is occupying four of six office floors of the building and has filled them with artifacts, design nods and "Easter eggs" tied to the Detroit automaker's history.

They range from a blueprint of GM's iconic design dome and an early map of its nearby proving grounds to an interior wallpaper of 300 patented technologies and a decorative wall of cassette tapes with songs featuring the automaker's brands as well playful references to executive stalwarts such as CEO Mary Barra and President Mark Reuss.

"Leadership asked when we were helping design the space to bring in some Easter eggs and details to represent who we are at GM, you know, honoring our culture and our history and our innovation," Rebecca Waldmeir, GM industrial design architecture and experience manager, told CNBC during a tour of the new headquarters.

Other surprises include references to relevant Detroit streets, design influences from GM's famed design campus in suburban Detroit and artwork and sculptures of its products.

Aside from the aesthetics, GM officials say the new offices will assist with collaboration and are more relevant to how the company expects its employees to work in a post-pandemic world. It will house executive offices and other corporate functions such as marketing, legal and finance.

"A headquarters really should be, at some level, a beacon for the culture of the company," said David Massaron, GM vice president of infrastructure and corporate citizenship. "When you come in here, it should help people understand who we want to be."

The new headquarters marks a significant square-foot reduction for the automaker's corporate office — from a towering complex called the Renaissance Center along the city's riverfront to just four floors, roughly 200,000 square feet, in the new building.

GM's new HQ is less than a mile from the RenCen, as it's commonly called, which has been a symbol for the city since, ironically, Ford Motor built the complex but decided not to make it its headquarters in the 1970s. GM purchased the building in 1996 as its third headquarters, all of which have been in the Motor City.

The RenCen is Detroit's fortress, a 5.6-million-square-foot complex complete with a more-than-700-foot center tower surrounded by four 500-foot towers and two smaller adjacent ones.

The complex is infamously difficult to get in and out of and to navigate. For much of its existence, it was surrounded by concrete barriers before a redesign around the turn of the millennium.

It has long been something of a physical permutation of GM's historically siloed culture, which Barra has made a priority to change during her roughly 11-year tenure as CEO.

"The RenCen was designed in a different era, in a pre-Covid era where everybody went to work five days a week, everybody went to their desk," Massaron said. "Particularly, in a post-pandemic world, you need office space that people want to come to, because we have options."

GM's roughly 50,000 U.S. salaried employees are currently required to work in-office Tuesday through Thursday, but the rules are more flexible than before regarding location and remote working.

Most of the company's new executive offices on the top floor of the building will be open for executives to use as they please, Massaron said. Only four of the offices will be permanently assigned to top GM executives, such as Barra and Reuss, he said.

GM declined to disclose how many employees are expected to regularly work at the new headquarters, saying foot traffic will fluctuate based on priorities and workflows. The company also declined to disclose financial details of its 15-year lease at the new headquarters.

The building complex, known as Hudson's Detroit, is owned by a real estate company of Rocket Companies chairman and billionaire Dan Gilbert, who has been purchasing and renovating properties in Detroit for more than a decade.

Aside from the office areas and the executive floor, which all overlook an open atrium, GM also plans to open a semi-public space to display products and host events on the first floor of the building.

Other amenities include social gathering areas and lounges, food and beverage services and a pickleball court and recreation area.

GM's new headquarters, which remains under construction, comes months after Ford christened a new 2.1-million-square-foot global HQ and product design and development center in nearby Dearborn, Michigan.

Ford's new facility includes offices, design and industrial operations and a host of amenities such as a 160,000-square-foot dining area with eight "kitchen concepts," multiple courtyards and other upgrades.

The notable difference in the size between GM's and Ford's new headquarters comes down to location, headcount and the automakers' portfolios of offices and operations throughout the region.

GM, for example, has a vast technology and design center that occupies 710 acres in nearby Warren, Michigan. That campus houses more than 24,000 employees.

Massaron said GM didn't feel it needed to create "a city within a city" for its new headquarters, because it's actually "a building within a city."

Here's a look inside GM's new world headquarters: