We certainly enjoyed our subterranean vacation, circling and bumping in the dark corridors and abandoned dens beneath the elegant city, despite young Daniel's howling for the sun. Admittedly, we had not expected to remain underground for the entire two and a half damp weeks of our visit - the brochure had not mentioned this fact, only glistening pools and elegant corridors, wide open spaces and the rush of wind. Luckily, these attributes we did discover once below, to our surprise. In fact, fully adjusted to the reduced light filtering through the chutes and the recycled air breezed back and forth under our noses by the passing subway cars, and once a suitable mattress was found squirreled away in a tranquil nook, we did find the amenities if not exactly meeting our expectations, then at least not inducing general panic. This cozy family kept cozy. No great complaint there.

At first we were discouraged to see only kiosks selling cheap, pre-fab croissants and yesterday's international press. But after a few days of searching the side passages, after butting heads against more than one dead end, false passage or barred gate, we learned which less-traveled corridors offered the best pickings. Here was a shaft that led towards the surface, and after a brisk climb up an iron ladder set into concrete, the upper reaches revealed a dim alcove covered by a sturdy grate that blocked full view of the sidewalk action above. This secret "boutique," as I like to call it, did a brisk business in spare change, half-smoked cigarettes (still smouldering, to my delight), and other accessories. I picked up a lovely deep red, calf's leather dress shoe for my sister back in Omaha, in fine condition, and I can say with confidence I wasn't even in the mood to shop.

Our Daniel took pleasure in racing his three-wheeler up and down the smooth hallways, always delighting in the sound of his new "loud voice" amplifying among the bustle of commuters and passed out beggars. A kindly accordion player, though clearly just recovering from a long night circling the city by train, offered to push his tricycle more than a few times along a particularly lengthy stretch, Daniel upon it like a knight astride a shining steed. Needless to say, the man received a big tip from me after, of course, playing a rousing version of a smart gypsy tune whose name I never did catch. Never did remember much of the native tongue, that due to several semesters of lazy study two dozen years ago and the lack of forethought to bring a phrase book.

No matter. Even Helen took to her new surroundings, helping the fruit man arrange his mangoes and pick through the browning cherries before he raised the metal door that signaled his stall "open for business." On occasion, she joined him in barking out the special of the day, whether it was five avocados for ten of the local currency, or a kilo of bananas for half the previous day's price. She'd be the first to admit feeling a sense of accomplishment when she and the fruit man sold a particularly iffy lot of lettuce, or a had satisfied a nervous homemaker's desperate search for a ripe pineapple suitable for serving same day of purchase.

As for me, I liked to slowly stroll the quieter passages away from the "day-timers," as we came to call them, once the underworld's pace had slackened. I even avoided the night guards with their ferociously stout muzzled dogs and leather-wrapped batons, and the bevy of weary ticket checkers, though both groups were nice enough. No, I took pleasure in examining the Art Nouveau tile work announcing a train line, or a particularly well-crafted water spigot where a bum - and weren't we all bums that vacation? - surreptitiously filled a jug or refreshed an evening face.

I became fascinated by the complexity of the entire network, my lack of detailed information creating not confusion but rather spurring a rejuvenated interest in deconstructing the surroundings of our vacation spot. What indeed was the reason for a particular ceiling pattern, and why was it engineers had determined this subway stop demanded renovation (water damage repair, new tile, fresh cement or paint, a new organizing principle for signage and ornamentation) while others remained untouched, or perhaps touched only on the drawing boards of municipal planners? I wanted to know. In my travels I became obsessed with understanding not just what but why; I got down on all fours to sniff out an offending odor and its origin, I ascended water-slicked tunnels into ante-chambers to determine the whereabouts, if one existed, of the heart or brain of the hive.

Of course an added benefit was riding the subway for free - well, to be true, for the price of one ticket. It was the best deal of the entire vacation. And I never tired of the stops and starts, or the endlessly variable crowds, a subset of which became my compatriots, if only for a few moments. Each individual path under the metropolis captured my thoughts: where was each headed with such bored determination, what thoughts traveled the intestines within their craniums, and what force kept them linked, intermittently, with their fellow voyagers, only to split them apart like atoms in an accelerator, or mix and match them in infinite combinations throughout their days. They were like rabbits inhabiting a warren with multiple holes, entrances, escape routes, back doors and false homes. They could pop up anywhere they pleased, or duck back down in times of danger to regain their acquaintance with the dim.

I was at times saddened by reminders of the outside. Seeing the commuters depart the singing cars and trudge up steps to the world above made me long for an even wider and unrestricted existence. Faint smells of whatever tree or flower must have been in blossom at the time - magnolia, say, or jasmine - would unexpectedly sift down to me, carried among the fibers of overcoats and in the folds of newspapers, able to momentarily overpower the urine and cleanser stench that I had come to accept as an emblem of home. Those moments I took to be tests. Did I have the strength to deny what my mind and body craved? What results occurred after a lengthy denial of vitamin D? How long could I go without reliable news from home? None of it bothered me. I knew I was becoming stronger, even as my eyesight strained and my skin shifted to the pallor of a cave dwelling fish. I became an explorer, a mole-ish expatriate, a world-class endurance athlete for a sport not yet accepted by the major sanctioning boards, a champion spelunker, a scientist of the realm beneath our feet. I didn't require corporate or federal sponsorship. Just my nimble mind, a few pencils, my notebook, flashlight and a dry hat.

Towards the end of the vacation, Helen and Daniel began to get squeamish and a bit bored. Papa, this is fun but what about baseball season? Can I have my birthday party here? Honey, the garden? The new school year's going to start in three weeks and Daniel's moving up to second grade. And there's the booster club, Labor Day with the folks, and aerobics. My sympathies were with them, I admit. But I had so much work to finish. The scholarship on the sub-city was so lacking. I knew of the abstracts and proposals I could write. The notebooks that begged to be filled. I was only beginning to taste the pleasure of studying the unknown, which lay before my eyes and hands like a vast black mirror, black only due to lack of light. One only needed to hold a candle to see the waters reflecting back. To know an opening, as in a map slowly revealed one distinct section at a time.

First, I wanted to make a study of graffiti: which tag had arrived first, which messages had fallen out of favor in exchange for new, and how to classify the various techniques and materials, colors and conditions, of the warring name-making clans of the natives. There was the numbering system used to identify the poster-sized advertisements which had to be cracked. I had not yet found the source of a stream that had bubbled by a junction between lines 7 and 12. There was the archaeology of subway maps, which are glued directly over the preceding map - in some places, ten or more versions thick. A flock of very confused sparrows had made their way down six flights of stairs to the electrical sub-station that supplied power to the entire central sector and I wanted to know, first, how they got down there and second, that each one of them was uninjured. Who knew the lexicon of conduits and wires, drip gutters and drains - where did they snake to and why? And then the small matter of the fortune teller's handbills, trampled on the dark floor by ignorant feet: who would spell out that history? Besides, I had some business to settle with the Homeless Federation, whose annual meeting went by without even a nod in my direction.

My last traveler's checks were cashed soon after Helen, with Daniel in tow, demanded to go home. I let them go - their lives beckoned above. As for me, I believe I'll be O.K. My life's just beginning down here among rushing sounds and mysteriously scented breezes. If I close my eyes, I can almost remember the elegant shape and deep hues of trees, those tiny rooted things fastened to the impeccably anointed parks above me, whose roots do poke into my new realm. I open my eyes, watch the swirl of color drain from my eyelids, and the ghosts above finally disappear.

Ethan Gilsdorf lives in Paris with his wife Isabel and takes the STRANGEST vacations.