The site is huge, about four city blocks long by two to three wide. Hundreds of workers dig with picks and shovels, dusting items off or rolling wheelbarrows up wooden planks.
Walking around, workers kick up pieces of ancient pottery and bones. Most of the items are ancient trash: broken pottery that sailors tossed from a ship or animal bones from a nearby slaughterhouse that were thrown into the harbor.
Digging for the Marmaray tunnel has also led to archaeological finds in the Uskudar district on the Asian side of Istanbul and Sirkeci and Veznedar on the European side. Giant machines constructing the tunnel are dredging up artifacts from the sea floor in the Bosporus.
Most of the tens of thousands of pieces likely to be uncovered will be cataloged and then reburied where they were found, said Metin Gokay, a scientist at the Istanbul Archaeological Museum. Only a small percentage will qualify as museum-quality pieces, while others will be used for research.
Modern-day Turkish coins will be left with the reburied items as markers to show the area has been disturbed, just in case archaeologists many centuries later dig the site up again, Gokay said.
Part of the value of the site is its abundance of ancient trash. Refuse is one of the best ways to study how people lived.
Hundreds of cracked clay pots already have indicated how merchants carried wine, olive oil and other trading items, and some carry markings that give clues about how the pots were handled and traded.
"We've found things that shed important light on the history of Istanbul," said Ismail Karamut, head of the archaeological project.
Officials said they plan to build a museum on part of the site and incorporate it into the rail project, which is meant to ease traffic on the jammed streets in the city of 15 million people.
The excavation site is where the Marmaray tunnel was supposed to link up with a subway station in a massive underground station. Planners now say they are considering moving the underground link to a spot farther outside Istanbul.
All around, the ancient is hemmed in by the new. One partly revealed structure is thought to be a church, but the archaeologists would have to dig up the other half to be sure — and it's under an apartment building.
