I first saw the Parthenon on a lovely autumn day in 1986. As we arrived at our hotel it was gleaming up there before us on the Acropolis of Athens, every bit as stunning a sight as I expected it to be: the elegant marble columns, the flawless design, the spectacular site at the edge of the famous hill. "I can’t believe it’s really there," said my wife Karen, who, like me, had known the world’s most beautiful temple only from photographs. But it was. Rising right above us, just a couple of blocks away, it glowed like a beacon.

The ravages of time had made it, of course, something less than the perfect structure it had been in the days when Pericles, Sophocles, Socrates, and Plato strolled the Acropolis. Early Christians had hauled away the colossal ivory-and-gold statue of Athena and reconstructed the building’s interior to make it suitable for a church. The Turks, when they captured Athens in 1478, had tacked on a minaret and converted it into a mosque. Later they used the building as a gunpowder warehouse, which exploded during a Venetian bombardment in 1687, wrecking the structure’s middle and blowing off its roof. The Venetians then tried to haul away the sculptured horses from the west pediment, making a mess of the job, and most of the remaining statuary was carried off by Lord Elgin in 1801 to London, where it is still on display at the British Museum.

Nevertheless, what remains of the Parthenon is still one of the noblest sights on this planet. Karen and I, trudging around in its battered and rubble-strewn interior the next day, the umpteen-millionth tourists to do so over the centuries, were as astounded by the damaged building at close range as we had been the day before when viewing it from the street below. Perhaps it was even more powerful a sight in its maimed condition than it would have been in all its original perfection: intact, it might have seemed implausibly and excessively beautiful, unconvincing, even unreal, a mere Hollywood confection. But the fact that its glory still was able to shine through, overwhelming despite all that the building had suffered, was better testimony to the genius of its builders than if it had been entirely unscarred.

I haven’t been back to Athens in the intervening decades. But apparently the Parthenon gets to look a little more like its original self every year. Archaeologists have been picking through the rubble heaps that Karen and I saw in 1986, trying to piece together the fragments of shattered columns. With the Olympics due to return to Athens in 2004, a plan had been put forth to reconstruct the six fallen columns of the east porch, and public pressure had mounted to restore the interior structures of the temple too, and even the lost roof. An outcry from architectural purists followed, and eventually a compromise emerged: three of the columns would be rebuilt, and three left as stumps. This has now been done.

The trouble is that the three new columns, even though they include much of their original marble, are a bright white. The remainder of the Parthenon, stained and pitted by the centuries, is a pinkish gray. The restorers now are experimenting with a mixture of mud, tea, and ferrous oxide solution to provide the three columns with a look of age. As for the ruined remains of the inner sanctuary, they are so fragmentary that the archaeologists don’t agree on which pieces should go where, and little has been reconstructed so far.

Eventually, I suppose, we might see a shiny full-scale replica of the Parthenon sitting atop the Acropolis where the old one used to be. How good an idea, I wonder, would that be?

Those needing to see an imitation Parthenon can see one right now, by visiting Nashville, Tennessee, where a full-scale replica was constructed in 1897 to mark the city’s hundredth birthday. It’s a handsome building, just not Greek, nor very ancient. It certainly is real, though, made of genuine stone, not a computer simulation, not a projected image. But the older one in Athens carries an extra level of reality, since, after all, it’s the original model, and though it isn’t quite as pretty as the one in Nashville it is generally thought to have a certain nobility and grandeur precisely because of all that has been done to it. Its injuries offer profound testimony of the accretions of history through time.

I’ve traveled widely through what we have come to call the Old World, and I’ve seen plenty of renovation jobs, ranging from the minor shor-ing up of a precarious wall to the complete reconstruction of some essentially ruined site. On the island of Crete, at Knossos, I wandered through the palace of King Minos, 3500 years old, that the great archaeologist Sir Arthur Evans excavated and restored a century ago. It’s an astounding site, but perhaps a little too astounding, because later archaeologists, working to a more exacting standard than that of the nineteenth-century pioneers, have shown that Sir Arthur may have done as much reinventing as he did reconstructing. Much of the palace of Minos, even the famous frescoes showing lithe dancers leaping over charging bulls, may have been built from scratch, reflecting Evans’ views of how things ought to have looked. The results are breathtaking. But such Hollywood movies as Cleopatra and Spartacus gave us breathtaking views of the past, too. We are very impressed, but we still can tell the difference between a movie set and a newsreel of the authentic ancient Rome or Alexandria. Such remodeling as Sir Arthur Evans’ work at Knossos blurs the line for us as we try to re-experience the broken past.

Then there’s Dresden, which was destroyed by a horrendous fire-storm during World War II. Its beautiful eighteenth-century pal-aces and museums have been rebuilt to the original design, largely using the original stones, and work is proceeding now on the last step, the reconstruction of the cathedral out of what was a huge pile of numbered stones when I was there in 1997. Is what we see today the "real" Dresden of the baroque era, or a Disneyfied replica, or something in between? What about the newly glistening frescos on the ceiling of the Sistine Chapel, brighter now than they have been for centuries, perhaps brighter than they ever were? What about the paintings we see in the great museums, retouched over and over by the brushes of artful or not-so-artful restorers? Are they still the originals? The same can be asked of Berlin, where many buildings damaged in the war have been rebuilt to the old designs, and Rome, where considerable subtle reconstruction has shored up the ruins of the great monuments of the Caesars, and, indeed, at most ancient sites around the world, where encroaching vegetation has been stripped away, fallen walls re-erected and supported by hidden metal bars, statues rebuilt, often fancifully.

There are valid arguments to be made for doing this, and arguments just as valid for leaving the ruins alone. Will rebuilding the giant Buddhas of Bamyan, destroyed by the Taliban, give us anything more than a theme-park imitation of what was lost? I don’t think the Parthenon as I saw it in 1986 needed any improvements, but what if the whole thing had been obliterated, rather than merely damaged, by that powder-magazine explosion three centuries earlier? Would the Greeks be justified in building a brand new Parthenon today, and would we revere it as we do the maimed but authentic one? It’s difficult to say. The past does inevitably disappear, and sometimes there’s value in constructing a reminder of what once had been, so long as we don’t confuse it with the original. Perhaps some sites should be stabilized against further harm and left otherwise alone, some partly reconstructed, and some built anew, but I wouldn’t want to be the one who decides what to do where.

The year before I went to Greece, Asimov’s published my novella "Sailing to Byzantium," which is set in such a far-future world that nothing at all remains of what we recognize as the past, and the people of the day amuse themselves by building replicas of five or six ancient sites, taking short holidays at them, and tearing them down to be replaced by other replicas. The story opens in Alexandria, where the Lighthouse, the seventh wonder of the world, exists again, along with the famed Library and all the palaces and temples. Then it moves on to Chang-an, an early capital of China, and then to the prehistoric Indian site of Mohenjo-daro, before concluding amidst the glories of Byzantium. Rome of the Caesars, a recent reconstruction, has already been dismantled, and so, too, has Timbuktu: "This is not a place any longer," my protagonist is told, when he tries to go there. And there is a full schedule of other sites to be rebuilt in the years ahead: Nineveh, Florence of the Medici, Babylon, Troy, Tenochtitlan, and even, perhaps, New York City, complete with its World Trade Center (this in 1985!).

But these far-future folk are indiscriminate in their attitude toward "reality." One of the five currently reconstituted cities, as the story begins, is Asgard, the capital of the Norse gods, which, so far as we know, existed only in Nordic poetry. And the reconstruction of Alexandria includes not only exact replicas of the Lighthouse and the Library but such fanciful creatures out of mythology as live centaurs and sphinxes. It is all the same to the reconstructors, fact and fantasy all part of the aggregate totality of the lost but still remembered past.

Perhaps it’s for the best that way. The past is over, after all. It lives on only as fragmentary bits of recollected memory, as more or less accurate accounts in books, and as broken remains of surviving structures. Why not mix a little fantasy in, for greater effect? We can never have the "real" past again. We can only guess at what it was really like; and all we have to go by are the fragments, which grow ever less identical to their originals every year. Eventually even the fragments decay beyond recognition or comprehension. Rebuilding them, reimagining what once had been, keeps the past alive, after a fashion, and perhaps that should be sufficient for us. Perhaps.