All right, here’s the scene:

I’m in Hugh Hefner’s back yard. That’s right, Joe Sixpack at the Playboy Mansion.

I don’t have to tell you, the place is crawling with half-naked chicks. And I ‘ve got my arms around two of ’em, Miss August and Miss December.

Smile, the photog says. The flash goes off, and like a blue bolt of lightning, two thoughts – as diametrically opposed as hot wax and a cold shower – race through the beery fog toward opposite hemispheres in my brain:

First thought: Life is good.

Second thought: Man, do I look stoopid.

It’s not an epiphany, intellectual self-examination being a noticeably absent response when confronted by Miss August’s astounding body.

Instead, it’s the confounding buzz every middle-aged guy feels when he finally lives out an adolescent fantasy. It’s like you’re in the middle of a beer commercial with your zipper down; this Bud’s for you . . . not!

Or, put another way, there is only one Hef, and I ain’t him.

Not that every red-blooded American male wouldn’t want a taste. Pete’s Brewing was rolling out a new line of ales and some marketing genius thought the press might actually pay attention if it held the event in the world’s most famous porn palace.

Imagine that, using sex to sell beer.

It sucked us in like moths to a pair of 42DD light bulbs.

“Who could resist?” Phil Baxter, a Los Angeles hotel manager who scored an invitation, was saying while surveying the skinfest. “This is one of those places you have to go in life. Mount Everest, the Great Wall of China, the Playboy Mansion – not necessarily in that order.”

Even if you haven’t thumbed through the magazine lately, this place is an indelible image in the collective unconscious of every man over 15. Barbi Benton lounging in a lace negligee against those stone lions . . . the girl next door skinny-dipping in the Grotto . . . Jimmy Caan and Tony Curtis and Bill Cosby schmoozing at poolside.

And Hugh Hefner – the pipe-smoking, square-jawed fleshmeister in silk pajamas and plush red smoking jacket – surveying his kingdom with two, three, a half-dozen gorgeous playmates on his lap.

Not long ago, the mansion scene was a tired cliche, nearly dying off in the late ’80s as the Playboy empire faltered. Blame it on the AIDS scare, anti-porn feminists, the Moral Majority or just a flaccid formula that lost ground to even raunchier competitors.

Whatever, the magazine’s circulation plummeted, its swank clubs were padlocked, the phallus-shaped casino in Atlantic City was sold. Hefner reached Medicare age and suffered a stroke. In 1989, the 63-year-old playboy did the unthinkable and pledged fidelity as he married 26-year-old playmate Kimberley Conrad and sired two sons.

But it’s the new millennium, baby. Viagra is on the shelf, and Hef is on the prowl.

At 75, he’s separated (Kimberley and the boys live next door) and swingin’. He’s said to be sharing his round bed with seven blondes, ages 19 to 28.

Suddenly, Hefner’s mack daddy to a whole new generation. Cameron Diaz, Leonardo DiCaprio, Cuba Gooding Jr. and Jim Carrey show up to be photographed with the septuagenarian. HBO’s “Sex and the City” filmed an episode at the mansion. Ruby Wax spent three days there, interviewing him for the BBC.

No such star power is on hand at the Pete’s Brewing party. Instead, the green lawns are filled with grazing beer execs and junketeering journalists, nudge-nudging each other at the sight of Shannon (Miss June 2000) Stewart’s gaping cleavage.

On this evening, unfortunately, the inside of the 29-room Tudor mansion is off-limits. Black-shirted thugs growl at me when I try to slide in the back door. I tell them, “I’m here for the orgy,” but they just glare.

The rest of the idyllic 5 1/2-acre property is open, though, so I head off toward a waterfall. The sun is setting, the sky is red, and the place looks like a very expensive postcard.

Why the hell, I wonder, would Hef decorate the back yard with kitschy pink flamingo statues? They look so real . . .

I reach down to touch, and the bird nearly rips off my hand. It’s alive!

I snatch back my arm before its nasty beak tastes blood. I turn, but my escape is cut off by another one of these avian raptors.

They work in pairs.

The quick-thinking photog tosses a plateful of hors d’oeuvres at them and we sprint toward the trees.

It’s only then that we discover the whole property is a freakin’ menagerie. Raccoons and peacocks mix with the guests. Monkeys in an outdoor cage grope for bananas and grapes. A cockatoo takes a slug from my beer cup.

“Follow me,” I say. “I know where we can hide.”

We make our way past the waterfall, to a pile of boulders that mark the entrance to a cavern.

The Grotto.

Now, others have blithely dismissed this spot as little more than a cheesy hotel hot tub – the sort of thing you’d find in a Poconos honeymoon resort.

These nonbelievers miss the point. This hidden cove is the very essence of the Playboy gestalt. It is the living centerfold, without staples.

Sculpted from stone and shimmering with cool water, the Grotto is cushioned for spontaneous casual sex. It is a private sanctuary where Jacuzzis tickle unsuspecting body parts and piped-in music (Ravel’s “Bolero”) tempts the shiest of nymphs. Champagne and steam numb the senses. Naked movie stars beckon. And, yes, the girl next door answers your every wanton desire. You are soothed and massaged and aroused in this place.

The Grotto is more than a den of iniquity. For a generation of healthy hetero males, it is the ultimate yet untouchable manifestation of carnality.

I gape like a teen-ager. An adolescent fantasy is within reach. I feel that buzz.

Nearby, another visitor – a San Diego radio DJ named Clint “The Morning Show Tool” August – is on the same wavelength.

“My God, I’ve been seeing this place since I was 11 years old,” says August. “You open up the magazine and see those girls. The first thing you say is, ‘Dad, where do Playboy bunnies come from?’

“He says, ‘The Playboy Mansion, son.’ ”

And now, it’s Joe Sixpack at the Playboy Mansion, where girls and dreams do come true.

I glance again at the Grotto. It’s tempting, but I’d be lying if I told you I took a dip.

-30-