HOLMBY HILLS, Calif. – For the first time since he purchased the Playboy Mansion in 1971 for just over $1 million, Hugh Hefner has opened the front gates of his mystical playpen to the paying public. Hugh Hefner is letting the public into the Playboy Mansion through a new E! reality show, set to debut Aug. 7.

And for a modest fee, sightseers will be allowed to tour the grounds of his gothic English Tudor and experience first hand Hef’s monkey cage, aviary, redwood forest and the much-whispered-about grotto where stars such as Frank Sinatra and Sammy Davis Jr. were said to have romped after dark.

But don’t go whipping out your AAA discount card just yet. Hefner’s home won’t open as a tourist attraction until after his death. And with a mother who lived to 101 and three twentysomething live-in girlfriends keeping him young at heart, the spry 79-year-old is still living life to the fullest.

In the meantime, Hef’s fans will get some early sneak peeks. PlayStation 2 has released a video game set at the Mansion, and Hefner is executive-producing an eight-episode E! reality series, The Girls Next Door (Aug. 7, 10 p.m. ET/PT) at his home, which explains the cameras and cables hanging from floor to ceiling.

Hefner, after entering his study wearing his trademark black silk pajamas and velvet burgundy robe, says he had just been reviewing a screenplay for a movie about his life written by Scott Silver (8 Mile) and to be produced by Brian Grazer (Cinderella Man). (He says he should be portrayed by someone boyish, like Johnny Depp.)

The estate, built in 1927, he says, is more than a home: “It’s a corporate facility and one of our most valuable assets; probably the most famous private residence other than the White House.”

And though he has been offered $75 million for the place, he has decided to keep it for posterity.

“The hope and intention is that it will continue after I’m gone and become a variation on (Elvis) Presley’s home (Graceland).”

To simplify his life (and allow for a more palatable premise for E! viewers), Hefner recently downsized his posse of seven girlfriends to “a very special three” – Holly Madison, Kendra Wilkinson and Bridget Marquardt.

“I’m emphasizing the quality these days,” he says of the women, who will join him in a Playboy photo spread in November.

But Hefner says his heart belongs only to 25-year-old Madison, whom he met 3½ years ago at a pool party at the Mansion. He invited her out on the town, and two days later, she moved in.

In a segment for the reality show, Madison (who has the famous Playboy rabbit symbol tattooed on the small of her back) leads a tour of the grounds, which also have a tanning salon, a game house (with a mattress floor) and a menagerie of caged and free-roaming birds and beasts.

A separate home across the street houses playmates and visiting playmate hopefuls. Hef calls it “a halfway house.”

His estranged second wife, Kimberley Conrad, and their sons, Marston, 15, and Cooper, 14, live in an adjoining house.

Hef blames his 1989 marriage to Conrad (the two separated in 1998 but never divorced) and his then-more-settled lifestyle for a drop of public interest in his empire.

“I’d been off the scene for about 8½ years when I came back as a bachelor,” he says. “I believe a whole generation had been waiting for me to come back out and play.”

That’s why he’ll most likely never marry Madison, who says she’s comfortable with the arrangement she and Hef share with Wilkinson and Marquardt.

“In the past, things weren’t so great,” Madison says, though she won’t reveal what went on (or goes on) behind closed doors. “My lips are sealed. What happens at the Mansion stays at the Mansion.”