What’s most essential about cities like Manhattan, Paris and London are not their endlessly variegated tiers of high and low culture, their multitudes of peopledom, or their architectural majesty.  Those things are real nice, don’t get me wrong.

But for me, what is most essential, are their underground transportation networks.

I’m by no means poo pooing the bus systems of these metropoloi.  I think we’re all old enough to know by now that a bus can save your ass in several situations, the first being when you have to get through the park in the late afternoon and all the cabbies have gone off-duty to spork styrofoam’s of Halal into their faces while smoking up freshly smuggled opiates and not showering.

The second is when for some god-forsaken reason  you’re in “bad” hood, and a gang of rabid 15 year olds wielding quarts of malt liquor are pointing at you and growling.  Hopping on 10 in any direction is far more pleasant than having a skateboard embedded in your cerebral peduncle.

The third is when you’re in a must-have-cell-reception scenario. Say a big money call is pending, or perhaps your wife is moments away from popping out a critter– being incommunicado for the 40 minutes it takes to get from 96^th to Franklin st. will land you in the chateau bow wow for who knows how long.  In the 60 minutes it takes on the m5, you got full bars, baby.

But the subway in NYC, the Metro in gay Paris, or the underground, as it is known, in the hard day drinking London is what ultimately makes each city unique.  Mind the gap!

Though most of the slobs who ride it don’t realize it, there’s an unconscious metaphor that taking the train inspires. In complete contrast to the turbulent, deafening scowls with which these rusty car thunder us through the earth, subways offer us an unrelenting myriad of sexual fantasies.

There’s nothing so erotic, or cinematic, as the filmic flickering of spark-light splashed onto the glistening legs of an anonymous yet ingeniously dressed woman.  Chamonix , red leather, knee high slit-skirt and open back Eva Franco halter top on say, a rainy day in mid to late May?

Reading The Post’s pillories on the latest Jets/Rangers/Knicks loss takes a fast second, third and forth place to imagining her Nine West heals stepping all over the root of your tongue.

This particular lady strode onto the stainless steal car without hesitation or invitation, like some seraphim from a once-and-future wet dream, and sat down across from me in full view of all who cared to lay ogle upon her, which was every heterosexual man within sniffing distance.  Actually, you can add women to that too.  You know a lady is smokin’ when other women stare.

And you don’t have to be Fellini to understand that a train ploughing through a tunnel is as good an excuse to get your fantasy on as any.  Especially when the conductor is jerking you to and fro at every screeching station stop.

But by the time you’ve fashioned a half-acceptable icebreaker, she’s up and striding toward the exit with the same causal aloofness with wich she’ll greet the undulating throng of subterranean commuters.

And as the car doors slide shut, just before the piercing, incomprehensible public address static deafens you with misinformation, you catch one last licentious glimpse of those calves, those epicurean calves, ebbing and flowing towards their final destination.

Yet before this happens, during that in-between time of furious dispatch, when fixtures oscillate and rattle above the remorseless tungsten rails that keep it all so steadfastly disciplined, there’s that precious few moments of self-induced phantasmagoria no subway-less city can provide.

Neurons fire potentialities at the same breakneck speed with which we’re all collectively traveling: where has she come from? Whither shall she land? What primary color might her thong be?  Is she as skilled as I, in hiding her desperate, erupting horniness, or just entirely apathetic?

The train pulses into an unanticipated bend, shimmying every last kilogram of fat-free flesh upon her, and then comes to a gagging halt that nearly brings her Nivea scented skin into contact with mine.  Her clean pressed hair masks the rush hour sour, as her darting eyes scan the proletariat for an empathetic smile.

I avert my gaze from the shabby tabloid, doing my damnedest to appear as non-chalant as the rest of the defeated strap-hangers in the presence of this graceful apparition.  But a nano-meter beneath the surface, I’m this close to asking her for a minty fresh something or other, hoping to the high heavens she might respond with, “Funny, I was going to ask you for one.”

We’d both resist the urge to giggle, then giggle heartily, embrace lips and forfeit our predetermined plans in order to flee to whomever’s dwelling is closer, shower off the filth of our decaying Interborough Rapid Transit system, and make love till our sexual organs redden with soreness.

But alas, when I snap back from my sexual chimera, my lady is gone, replaced by a Balkan looking fucker whose body odor is so pungent that it actually has a shape.

I trudge to another car and see a beautifully caramelized Hispanic woman knitting an automatic weapon.  My mind begins to race once again.  She could be the one: so gorgeous and foreign and edible.  I wonder how many stops she has left to go and what she sounds like after being submerged in hot tub of chocolate mousse.