The excavation site was shown to the public on Monday, when details of the permanent display project were also announced. Several of the large marble paving stones were etched with children's board games, while others were marked by horse-drawn cart wheels.
Also discovered at the site were remains of tools and lamps, as well as the bases of marble columns.
Viki Tzanakouli, an archaeologist working on the project, said that the Roman road was about 1,800 years old, while remains of an older road built by the ancient Greeks 500 years earlier were found underneath it.
"We have found roads on top of each other, revealing the city's history over the centuries," Tzanakouli said. "The ancient road, and side roads perpendicular to it appear to closely follow modern roads in the city today."
About 23 feet below ground in the center of the city, the ancient road follows in roughly the same direction as the city's modern Egnatia Avenue.
In 2008, workers on the Thessaloniki metro discovered more than 1,000 graves, some filled with treasure.
The graves were of different shapes and sizes, and some contained jewelry, coins or other pieces of art.
A massive excavation project also took place during the 1990s in the capital, Athens, before the city's new metro system opened in 2000.
Thessaloniki's new subway is already four years behind schedule, due to the excavation work as well as Greece's financial crisis.
Thirteen stations will operate initially, before a 10-station extension is added later.