A floor mosaic from one of Roman Emperor Caligula's opulent private ships, which was stolen after World War II, is on its way back to Italy from the United States where it has been recovered from a private collection.

A floor mosaic from Roman Emperor Caligula's opulent private ship, which was stolen after World War II, is on its way back to Italy from the United States

The first century AD marble, serpentine and porphyry mosaic came from one of Caligula's ceremonial vessels, which was found at the bottom of Lake Nemi, near Rome, in the 1930s.

The artifact, stolen from Italy's Roman Ship Museum after the war, was seized by the New York district attorney's office from the collection of Helen Fioratti.

She and husband, Italian journalist Nereo Fioratti, purchased the piece more than 45-years-ago from an aristocratic family that lived on the lake.

'They thought they owned it. We thought they owned it. Everyone thought they owned it,' she said to NBC News of the confusion of ownership.

While it was unknown to the woman how much they paid for the piece, they assume that it cost them thousands of dollars and was a 'completely innocent' purchase.

The Italian military police's Art Recovery Unit was responsible for seizing the ship piece, and Fioratti believes a recent magazine feature is what alerted authorities to its whereabouts.

The first century AD marble, serpentine and porphyry mosaic came from one of his ceremonial vessels, which was found at the bottom of Lake Nemi, near Rome. The artifact, stolen from Italy's Roman Ship Museum after the war, was seized by the New York district attorney's office from the collection of Helen Fioratti

'We had our apartment featured a long time ago in Architectural Digest and I'm sure there was a photograph of the table in front of the sofa,' she added.

The piece was ceremonially returned to the Italian government based in New York.

'The United States have today given back to Italy several archaeological treasures that came from clandestine digs or thefts in our country,' Culture Minister Dario Franceschini told a news conference in New York on Friday.

'The United States have today given back to Italy several archaeological treasures that came from clandestine digs or thefts in our country,' Culture Minister Dario Franceschini told a news conference in New York on Friday

'They will all be returned to the places from where the criminals took them,' he said.

According to the Manhattan district attorney's office, no criminal charges have been filed against Fioratti.

Among other Roman-era items recovered was a vase from the Puglia region dating to around 350 BC, which found its way to the New York Metropolitan Museum, and two amphorae from the 4th or 5th century BC.

The vase was taken from an illegal dig in the 1980s.

The artifacts presented at the news conference also included Roman coins, books and manuscripts.

Caligula, whose real name was Gaius Julius Caesar, was emperor between AD 37 and AD 41. Historical accounts describe him as an insane, violent and sadistic man who ordered killings at a whim. Legend has it that he planned to make his horse Incitatus a consul.

The tile is believed to be part of one of two of the emperor's lavish ships.

The tile is believed to be part of one of two of the emperor's lavish ships. Over 230ft long and 65ft wide, the ships had difficulty navigating through the volcanic waters of Lake Nemi and would eventually sink there

The marble flooring was found during excavations between 1928 and 1932

Following WWII and the end of fascist dictator Benito Mussolini, it is believed the tiles were looted from the museum they were housed in and eventually made their way back to the aristocratic family on Lake Nemi

Referred to as 'floating palaces' by the Museum of Roman Ships - home to pieces of the ships - the boats were said to be home to parties that took place over several days.

Over 230ft long and 65ft wide, the ships had difficulty navigating through the volcanic waters of Lake Nemi and would eventually sink there.

The marble flooring was found during excavations between 1928 and 1932. Following WWII and the end of fascist dictator Benito Mussolini, it is believed the tiles were looted from the museum they were housed in.

And for Fioratti, the idea of people not being as interested in the piece as they were when it was in her home, was too much for the dealer to bear.

'I don't know if anyone is going to see it as much as they did in my place. I had people who were interested in antiquities admiring it in my home all the time. Now it will be in a museum with a lot of other things,' she added.