SAN FRANCISCO (Map, News) - When you can afford to have an original sculpture by Alexander Calder unassumingly taking up space on your office table, as Gap founder Don Fisher does, you can also afford to be more than a bit understated.

“It’s a good collection,’’ he says of the contemporary art pieces he and his wife Doris have been amassing for the last three decades. “And I don’t want to see it in the basement.’’

That, in a nutshell, is the crux of his decision to build his own museum in the Presidio and finally put on display what only people who enter the Fishers’ private and corporate lives have so far seen — one of the finest modern art collections in the world, soon to be coming to a national park in San Francisco.

Much has been made of the fact that it seemed a natural fit for the Fishers to donate their collection to the San Francisco Museum of Modern Art since they have been major benefactors and trustees for SFMoMA and there was the space available to add a new wing to the existing museum for their collection. But obscured in the telling is the reality that museums insist on control over their collections and shows — something which donors give up in the transfer.

I can’t imagine that anyone with an art collection estimated to be worth at least $1 billion would cede input on how and where it is displayed, and after months of talks with officials from SFMoMA and the de Young Museum, that is the conclusion reached by the Fishers.

“It basically came down to what kind of curatorial control my wife could have,’’ Don Fisher told me in his 15th floor office at Gap headquarters on the Embarcadero this week. “We wanted to have some involvement with the collection during our lifetime.’’

Control — and history — plays a part in the decision to place the museum on the main post at the Presidio, where Fisher served as one of the original trustees on the quasi-federal agency which oversees the former Army post. The Presidio Trust will make the decision on whether Fisher’s proposed museum gets the green light — a good bet for anyone who knows San Francisco — and one can only imagine the cries about corporate giveaways, the evils of public private partnerships or The City caving at the hands of “downtown business interests’’ if Fisher tried to get approval for the museum from the wacky band of brothers known as our local legislative officials.

As it is, my sources at City Hall tell me that when Fisher was talking to de Young Museum officials, who had to run the gantlet of city politics to get approval for their new building, he was essentially told the Board of Supervisors would never let another structure be built in Golden Gate Park. Fisher wouldn’t address it when I talked to him, but certainly his desire to focus on the Presidio makes perfect sense in that scenario.

His only comment on the talks with SFMoMA and the de Young about moving the collection to new wings at those museums was: “It never got to the point where everything got into place.’’

So despite the off-base criticism of Fisher’s museum plan from the ideologically bound, San Francisco appears poised to be the beneficiary of another great museum that should be a huge boon toward the Presidio’s required goal of being self-sufficient in the next six years. Even a brief glimpse of what awaits the public if the museum opens in three years, as planned, would quicken the pulse of any art lover.

In just his office area alone, Fisher has works by Claes Oldenburg, Cy Twombly, Ellsworth Kelly, several pop art pieces by Roy Lichtenstein and a series of portraits of Mick Jagger done by Andy Warhol. All told, there are more than 1,000 pieces in his and his wife’s collection, a veritable showcase of some of the greatest figures in contemporary art, which is why he felt that he didn’t have a lot of options but to build his own museum — at least if he wanted it all to be seen by the public.

“It’s too good of a collection to break up,’’ he told me. “The art world is very constrictive, and in this project I’m not as constrained.’’

If all goes as planned, the Contemporary Art Museum at the Presidio would open its doors in three years, a timeline that would likely have been tripled if Fisher had to clear the hurdles of The City’s strangling bureaucracy.

For a man who made much of his fortune on his canny knack of finding and buying real estate, he seems to have set on the right place to put a precious art collection on view — a base, not a basement.

Ken Garcia’s column appears Tuesdays, Thursdays and weekends in The Examiner. E-mail him at kgarcia@examiner.com or call him at (415) 359-2663.