ATLANTA  Should you wish to rent out the office of Rodney Mims Cook Jr. for a fund-raiser, say, or a wedding reception, he will happily vacate the premises, leaving a fire burning in the fireplace.

Most offices would not be in demand for such services, but Mr. Cook’s is special. It is a glass pavilion atop an 82-foot-high stucco-and-limestone version of the Arc de Triomphe in Paris, overlooking a small blue lake as if it were the grand finale to a miniature-golf course with an ancient Roman theme, surrounded by condominiums. The Millennium Gate, as it is called, stands in the middle of Atlantic Station, a large shopping, business and residential community on the site of a former steel mill near downtown.

“It’s wondrous and strange and fanciful,” said Alan Balfour, the dean of the school of architecture at Georgia Tech. “I don’t think anyone even knows why it’s there. It arrived from another planet, I think.”

It arrived, in fact, from the planet of Mr. Cook, 52, a buttoned-down member of a wealthy Atlanta family. For years, he has championed the cause of classical architecture, developing close ties to Prince Charles, a fellow enthusiast, and serving on the board of the Institute of Classical Architecture and Classical America. He is currently coordinating the design for the memorial to John Adams, John Quincy Adams and their wives planned for Washington.