MELISSA BLOCK, HOST:

In Istanbul, major public transit projects are under way after years of delay. The problem wasn't lack of financing but the layer upon layer of artifacts that tend to turn up every time the earthmovers get started in that ancient Turkish city.

NPR's Peter Kenyon has the story of one dig along Istanbul's southern shore. It's uncovered what experts say is a staggering array of artifacts from pre-Ottoman Constantinople.

PETER KENYON, BYLINE: I won't go on about how awful Istanbul traffic can be. Suffice to say that on my initial reporting trip here, I missed my first appointment by an hour and a half. So when a tunnel under the Bosphorus Strait, and the rail and subway network that will connect to it, were stopped in their tracks several years ago, eyes rolled and shoulders shrugged. Istanbul is, after all, one of those places like Rome, Athens, or Jerusalem where this kind of thing tends to happen a lot.

But local frustrations were soon overwhelmed by the sheer magnitude of what was being so carefully lifted from the mud along the Sea of Marmara: millions of pottery shards, animal bones - horses, elephants - 60 species in all. And many other remnants of the booming trade done here in the Middle Ages, when this dog-eared Istanbul neighborhood was the glorious port of Theodosius. To here, the world's rarities arrived at Constantinople, the eastern flank of the Roman Empire.

For archaeologist Ufuk Kocabas, from Istanbul University, it's the find of a lifetime.

UFUK KOCABAS: Up to now, we found 36 shipwrecks. This is the world's biggest shipwreck collection ever found. I can say, you know, their protection status, wonderful.

KENYON: With the transit projects back on track behind him after years of delay, Kocabas shows the visitors the timbers from the Byzantine vessels, now resting in huge tanks where freshwater is slowly circulating, leaching the salt from the ancient wood. It's a process that will take years, during which time Kocabas says the wood must be protected from new enemies, such as bacteria and mosquito larvae.

KOCABAS: That's why we are adding some biocides inside. Also, we are using goldfish. They are really efficient to larvae of mosquito. They like to eat this larva.

(LAUGHTER)

KENYON: The Istanbul Archaeological Museum is in overall charge of the project, with Kocabas and his colleagues taking care of the ships. They range from small cargo boats to mighty Byzantine naval vessels that helped break two Arab sieges and repelled other would-be conquerors.

KOCABAS: Yeah, in that time, their navy was really strong because they invented Greek fire; a kind of - how can I say - fire bomb, you know? And it was a secret.

KENYON: A History Channel documentary about ancient warfare sought to explain this terrifying weapon that spit flames that burned even in water.

(SOUNDBITE OF A HISTORY CHANNEL DOCUMENTARY)

UNIDENTIFIED MAN: This firefight in the 7th century AD used a large reservoir of liquid naphtha or Greek fire. The modern equivalent today would be napalm.

KENYON: It will take years to preserve and reconstruct the Byzantine fleet. And a new museum will be needed to display the vast trove of medieval finds. By which time, Istanbul commuters may be humming along under the new Bosphorus tunnel, or clinging to straps on a new subway line. I'm betting that traffic will still be miserable.

But archaeologists will be watching this very pro-development government's other projects, such as the new excavation under central Taksim Square, to see what wonders may await in this history-soaked corner of the world.

Peter Kenyon, NPR News, Istanbul. Transcript provided by NPR, Copyright NPR.