A girl holds a cherry inflatable mattress as she walks on the "Spiagge Bianche" (white sand) beach in Rosignano Solvay.

Holidaymakers splash in the turquoise waters of the Rosignano Solvay beach in Tuscany and laze on its pristine white sands -- most of them fully aware that the picture-perfect swimming spot owes its allure to a nearby factory.

"I discovered it on Google Maps," said Dutch tourist Lieuya, who travelled to the beach with his family to enjoy a setting more reminiscent of the Caribbean than of northern Italy.

The white sand and unusual Caribbean appearance is not natural.

"I was told it's not dangerous, that the colour comes from the soda factory next door," he told AFP.

Questions have lingered for decades over why the sea and sand are such startling colours -- with some environmentalists suggesting the phenomenon is caused by heavy metals emitted by the plant.

The beach, about four kilometres (two-and-a-half miles) long, is named after the Solvay factory.

Reflection of the sky

"Solvay was like a mother to this area of Tuscany. We called it 'mamma'," Leonardo Martinelli, a journalist born in the town and whose mother worked at Solvay for half a century, told AFP.

Belgian industrialist Ernest Solvay, the plant's founder, "guaranteed well-being by opening a school, a hospital and a theatre," he said.

The factory has ensured "the unemployment rate has always been low," he added.

Swimming is banned along a small stretch of the beach, but that is because of a strong current in the area.

The group's industrial director Davide Papavero told AFP the company "respects all the rules of a high-risk site".

"The plant... only discharges powdery deposits of limestone, a harmless substance that is safe for the environment, but explains the white colour of the sand," he said.

The startling blue of the water is caused by the reflection of the sky against the white sea floor, Papavero added.

Agence France-Presse