The mosaic floor was grand enough to grace an idyllic setting: a sprawling villa with sweeping views of the Mediterranean and the surrounding mountains near ancient Antioch. It was assembled cube by tiny cube around the third century A.D. in the villa's courtyard, and its wonders include rosy cherubs astride gamboling dolphins, their rods dangling in pursuit of darting fish.

The villa, known as the House of the Drinking Contest - for a mythological theme in another remarkable mosaic there - is no more. Only its foundation outlines remain, buried under farmland at a remote site in what is now southern Turkey.

But now, some 5,000 miles and 18 centuries away, the mosaic floor has gained a second life in a gallery at the Museum of Fine Arts here. Using special tools for slicing and chiseling, museum workers have already removed about 4,200 pounds of concrete that was poured onto the back of the mosaic for safe transport when it was originally removed from the site in Turkey.

As the conservators clean and restore the mosaic, piecing together the bits of glass and limestone known as tesserae and reproducing the border that once bound the floor's three panels, museum visitors are being treated to a ringside viewing.

"This is one of the few places in the world that you can actually see conservation work on Roman mosaics done in the public view," said Christine Kondoleon, the museum's George and Margo Behrakis curator of Greek and Roman Art.

The mosaic is one of some 300 floors that were uncovered in the Antioch area in the 1930's in a dig organized by Princeton University with help from the Louvre, Dumbarton Oaks in Washington, the Worcester Art Museum in Massachusetts and the Baltimore Museum of Art.

Antioch was then part of Syria, and conservators say that local officials kept roughly half the find, which can be seen at the archaeological museum in Antakya, the modern name for Antioch, now in Turkey. The other museums divided up the bounty. (Princeton owns the mosaic with the drinking-contest theme.)

After traveling to Dumbarton Oaks, the mosaic, which then weighed 6,600 pounds with its concrete backing, remained in its shipping crates for 65 years in a shed outside the institution's main garden. Dumbarton Oaks "has always had a very limited amount of space," said Stephen Zwirn, its assistant curator of Byzantine art.

Intrigued by the floor's impeccable provenance, the Museum of Fine Arts negotiated a purchase in 2002. (Both institutions declined to specify the price.)

Once the restoration is complete, scheduled for late 2006, the museum will use the floor as the centerpiece of a re-creation of an ancient living room and dining room to shed light on how the Romans - at least the affluent ones - in the eastern Mediterranean region lived.

Given the mosaic's size and complexity, it was clearly commissioned by a wealthy family who probably chose the theme and ordered it from a mosaic specialist, Ms. Kondoleon said. The courtyard was a center for entertaining, with reclining couches normally placed along the outer panels of the mosaic so relatives and friends could gaze upon its splendors.

At the center of the mosaic are the cupids on the dolphins. Their rods are cast into a sea brimming with luminous mullets, mackerel and wrasse in dark reds, oranges, yellows and lapis blue.

To Romans, fish tanks were status symbols. Some villas had freshwater tanks and some had saltwater ones, said John R. Clarke, regents professor of art history at the University of Texas at Austin.

In that era, fish were considered an expensive delicacy, Ms. Kondoleon said, and the Romans aspired to be connoisseurs. She cited a text from the fifth century B.C. mentioning an eel that cost a laborer three days' pay. Mr. Clarke mentioned one about a Roman who spent a fortune to bring a giant sturgeon back from the Black Sea, served at the table with a trumpet fanfare.

Beyond its prestige, the fish mosaic was possibly a source of whimsical amusement, Professor Clarke suggests. The little cupids were the children of Venus, the goddess of love, who is often represented in Roman art as a fisherwoman; as they cast their lines, they were undoubtedly trying to "catch love," he said. "It is like landing the big fish."