Italian police recovered a valuable Roman-era marble bathtub stolen from Italy after spotting it by chance in a Barcelona antique dealership, Spanish police said on Tuesday.

The officers, specialists in stolen artwork, were in the Spanish Mediterranean port city on other business when they stumbled across their find, which had been stolen from the garden of a villa in Rome in 2005.

The owner of the antique dealership said he thought the oval-shaped bathtub, was a modern copy of an antique.

He said he had bought it at the end of 2005 for €3000 from another dealer and had it on sale for a mere €6000.

In fact the bathtub, which dates back to the era of the Roman emperor Hadrian, in the second century anno domini, is worth a cool €300 000.

The only other surviving example is on display at the Vatican Museum.

Spanish police believe the bathtub, which weights half a ton, was transported to Spain by sea, most likely hidden in a shipping container.

It was handed over to the Italian authorities on Tuesday, they said.