A 1,800-year-old mosaic of toga-clad men dating back to the Roman era has been unearthed in Israel, archaeologists said on Thursday.

The mosaic was discovered during the excavation of a building from the Byzantine period — some 300 years younger than the mosaic it was on top of — in the coastal city of Caesarea.

"The surprise was actually that we found two beautiful monuments from the glorious days of Caesarea," said Peter Gendelman, co-director of excavation for the Israel Antiquities Authority, of the building and mosaic.

Caesarea was a vibrant Roman metropolis built in honor of Emperor Augustus Caesar by King Herod, who ruled Judea from 37 B.C. until his death 33 years later.

The excavated portion of the mosaic, which the antiquities authority said was 3.5 meters by 8 meters in size, depicts three toga-clad men, as well as geometric patterns and an inscription in Greek, which is damaged.

If the mosaic came from a mansion, the figures could have been the owners, or if it was a public building, they may have been the mosaic's donors or members of the city council, Gendelman said.

The mosaic was of a high artistic standard, with about 12,000 stones per square meter, the antiquities authority said.

Israel is undertaking the largest conservation and reconstruction project in the country in the Caesarea National Park, the antiquities team said. The project aims to reconstruct a Crusader-era bridge.