Cargill can lay claim to one of the corporate world’s unique headquarters: a lakeside mansion complete with a marble staircase and 13 fireplaces, all modeled on a French château.

But after calling the sylvan manor on Lake Minnetonka home since 1946, Cargill’s honchos will move down the road a bit to the company’s sprawling main office complex, an architectural creature of the 1970s. The relocation will occur within the next 12 to 18 months.

So why would leaders of one of the world’s largest privately held companies ditch their lordly digs for a standard office building? Primarily to get more modern and efficient office space, the company says.

Cargill’s main Minnetonka office is undergoing a big renovation that is expected to be completed a year from now. The nearby “Lake Office,” as Cargill calls the manse on Grays Bay, has had ventilation and communications updates over the years, but very little of the original structure has been altered.

Plus, top leadership of the 151-year old company wanted to be closer to employees. “I want to be near the team,” said Dave MacLennan, Cargill’s CEO since 2013. The Lake Office “is too quiet.”

About 40 people work in the Lake Office — calling it “the château” is frowned upon inside Cargill — while the main office has 1,642 employees. Cargill’s Hopkins office is even bigger with 1,960 workers, and the company has opened two new innovation and research centers in Plymouth over the past couple of years. Cargill has nearly 5,000 employees altogether in Minnesota.

The decision to relocate top executives comes at a time when MacLennan has reorganized Cargill’s leadership team, the most sweeping structural change in senior management in about 15 years. In December, Cargill dropped its old setup of two separate corporate leadership teams with nearly 30 people combined, and adopted a single 10-person group led by MacLennan.

It’s not clear yet what will become of the château, which was built in 1931 as a country home for Rufus Rand Jr., grandson of the founder of the Minneapolis gas company that became Minnegasco.

Rand, who built the Art Deco Rand Tower in downtown Minneapolis, got the château idea from his time in France as a U.S. aviator during World War I. Rand and his family lived at the mansion — which came with 17 bathrooms and was known as “Still Pond” — for just a decade before they fell on hard financial times.

John MacMillan Jr., scion of one of Cargill’s founding families, also served in World I in France. He took a liking to the mansion after the Rands left. So, Cargill bought it during World War II, and MacMillan and other executives moved there from the company’s headquarters in downtown Minneapolis.

In 1970, Cargill opened an office complex on McGinty Road that’s about a five- to 10-minute walk from the Lake Office. Over the next seven years, Cargill’s employees migrated to the new office from Minneapolis.

The Lake Office was criticized by some Cargill employees in a 2000 internal report on the company’s culture.

Newer employees in the main office seemed to view the Lake Office as a “secretive, unwelcoming place,” according to a 2006 history of Cargill by Wayne G. Broehl Jr. Midrange employees saw the same separation, calling the place “Versailles.” Long-term employees simply said, “Get rid of the Lake Office.”

Is that sentiment still around today? Cargill spokesman Pete Stoddart said no, and that Cargill employees view the Lake Office with “more pride than anything as it is part of our history.”