Where Ozymandias was quarterback

THE first astronauts saw the Great Wall of China from space - the only man-made feature so distinguishable. The earthbound tourist, traveling across plains ten miles or more from the wall can also see its crenellated top winding across dry hills.

But other monuments of departed civilizations are more cunningly tucked away in the jungles and crevices of Earth's crust. Petra, Machu Picchu, Tikal, Angkor Wat, the caves of Datong, and Canyon de Chelly give even the expectant traveler a start. They materialize suddenly - around a corner, beyond a liana vine, out of a smooth cliff face, or inside a half-hidden cave entry.

For a moment, the intrepid tourist - though surrounded by twenty other humans wearing 35mm zoom cameras, preposterous straw hats, and sling bags filled with reproduction Inca pots - can imagine himself Schliemann abruptly digging out the first glimpse of ancient Troy. Suddenness adds to the overwhelming historic and aesthetic impact.

To moderns, who live in goldfish bowls by rivers or harbors or at crossroads on the plain, the abandoned shell of a civilization hidden in a cranny of the earth's crust or half-swallowed in jungle is - there's no other apt word - breathtaking.

If you are a reader of travel literature, you know these hidden monuments are the big game your safari is designed to seek out. But if you are a real traveler you also know there is a generous sampling of tedium meted out on the way to your quarry. The tedium serves its purpose - a restful interlude between Parthenon and Nile temples, between Niagara and Yosemite.

The highway north from Sfax, on the coastal plain above the Tunisian Sahara, bores (pun intended) through a scene of such medium tedium. There are exotic sights fore and aft; but flatness in between. With two European journalists, I was being driven north from the great desert. We sped along at 90 kilometers an hour, crossing an absolutely empty landscape that could not possibly have concealed a surprise. No jungle, no cliffs to hide even a hut, much less a palace.

The Tunisian plain scrolled past our windows, mountainless, featureless except for wisps of grass, an occasional squat olive tree, and perhaps a stray goat, or a camel harrumphing across the far horizon.

Our caravan (one battered Simca) chattered along over the surveyor-straight road. We were lulled by the undeviating motion, eyes roving but expecting nothing. Heat waves made the dry air waver. At first seeing the emptiness undulate was intriguing. Landscape with vibrato. But soon it lost its novelty. Unfascinatin' rhythm.

My thoughts must have wandered for quite a while.For suddenly, off to the right there loomed what seemed the most fantastic mirage I had ever seen. An immense Roman coliseum sat heavily upon the empty plain.

What trick of the atmosphere could have transferred it there? We were some 450 miles across the Mediterranean from Rome.

To make the perplexing more so, this great stone stadium seemed more intact than the Roman original. There was a jagged gash in one side of its oval perimeter. But it showed less sign of erosion on its dusty pink-gold stones.

I tapped our driver on the shoulder and pointed. I half expected him to look puzzled, seeing nothing. But he grinned and said: ''Everyone he is surprise-ed by our coliseum. They always askin' me, 'Where are the houses, where are the city? Why zis coliseum out here all of alone?'

''Then they start sayin', 'How many people can sit in there lookin' at the gladiators and lee-ohn?'

''I tell zem,'' the driver continued, ''many tousand were sitted there just like your futball game.''

By now we were drawing closer to the amphitheater. At first we had not believed the driver's words about seating capacity. But it was obvious he was correct.

(We later learned the now-collapsed tiers of seats had held 30,000 Roman colonists and locals.)

We were drawing abreast of the magnificent structure - as startling in its own way as the pyramids. Perhaps more startling in one respect: The pyramids were constructed to serve the pharaonic dead. This great pile of cut stone was built to serve living, cheering

plebs. But where in this near-empty scene could tens of thousands of plebian Roman colonials and Carthaginians have come from?

Anyone who follows modern American football knows the kind of heavily populated suburbs in Long Island, New Jersey, or Arlington, Texas, where today's marketing geniuses tell owners to locate professional football stadiums. If the emperor across Mare Nostrum had ordered bread and circuses to keep the populace happy, surely some demographic expert had misled him in this case.

Our Simca pulled into the little town of El Djem. I could see that the driver had exaggerated in reporting the coliseum was ''all of alone.'' There were streets of small houses nestled under its imposing bulk. But not enough to fill the stadium with season ticket holders. El Djem's houses were more thoroughly dwarfed by the

mighty carcass than the Lilliputians were by Gulliver.

Before we could dismount to examine the coliseum, the driver took us to an architectural dig at the edge of town where excavators had laid bare the foundations of wealthy Roman villas of the third century.

There we heard the story of the ancient city of Thysdrus, once one of the richest of Roman colonial towns in the province of Africa. It drew its wealth from the soil - especially olive orchards. That wealth supported the stadium and its crowds. (Even today Tunisia exports much of its olive oil to Italy, whence it is re-shipped, usually with Italian labels, to cooks of Italian descent in the Western Hemisphere.)

When the emperors across the Mediterranean could no longer hang onto their empire with bread, circuses, guile, and colonial forays, Thysdrus withered. Walls fell. Winds buried the mosaic floors. Courtyards and fountains disappeared. And slowly the stadium lost its seats, long after the cheering and jeering that emanated from them had ceased.

Near the end of the 17th century or the start of the 18th, a local tax collector sought and got permission from the Bey of Tunis to use artillery to collect some tax rebels who had barricaded themselves in the coliseum. The tactic worked. (I hope no one from the Internal Revenue Service is reading this.) But the shelling left the aforementioned gap in the 120-foot-high triple-arched walls

That breach unbalanced the thrust of the arches in the great oval, and, had it not been crudely patched together, we might have been left nothing but a pile of rubble.

Although the stadium looks larger than its prototype in Rome - because of the contrast in scale - it is in fact slightly smaller (526 feet to 604 feet on the long axis) than the Roman model. But in any competition of ancient astrodomes it fares well. It is larger than the coliseum at Nimes, France, whose long axis measures just 443 feet.

Tramping through the ruin was almost anticlimactic. Entered, it lacks drama. Its great virtue among monuments is its total out-of-placeness on an empty horizon. Although it is the opposite of those earlier-mentioned wonders whose drama derives from their hidden-ness, it shares the eerie impact one experiences because a whole civilization is missing from the scene even though its daily movie sets are left behind awaiting the return of Aztec or Roman actors.

Afterward, as we sped on toward Sousse, Hammamet, and Tunis, the statistical competitiveness of the stadium-builders of Thysdrus, Rome, and Nimes rattled around in my head. For a moment it reminded me of the hometown pride which has driven stadium builders in our era on from Rose Bowl to Orange Bowl to Astrodome and King Dome, from Olympiad to Olympiad. In that light, it's amazing that Thysdrus's arena wasn't built a few feet longer than Rome's Colosseum. Just as the Texas state capitol has a higher dome than the capitol in Washington, the San Jacinto Monument is higher than the Washington Monument, and so on.

Fortunately all of those bowls and domes are part of vital, growing communities. The only thing Thysdrus should teach today's builders is that great civilizations cannot be apathetically presumed to be immortal. Their citizens must keep them vital - not overextended, or undermined by apathy and circuses.

The little Simca sped north. Suddenly the Oxford-trained German journalist in the back seat began to recite:

I met a traveler from an antique land Who said: ''Two vast and trunkless legs of stoneStand in the desert. Near them, on the sand, Half sunk, a shattered visage lies, whose frown, And wrinkled lip, and sneer of cold command, Tell that its sculptor well those passions read . . . . And on the pedestal these words appear -

'My name is Ozymandias, king of kings: Look on my works, ye Mighty, and despair!' Nothing beside remains. Round the decay Of that colossal wreck, boundless and bare, The lone and level sands stretch far away.''

Looking through the rear window, I found the ancient superbowl now little more than a dot on the southern horizon. We lapsed into silence, thinking about Ozymandias, how to keep civilizations alive, and dinner half an hour ahead.