It is "one of the best-kept property secrets in Italy", according to estate agents hoping to tempt British buyers, "alluring and unspoilt."

But "unspoilt", in the case of the central Italian region of Abruzzo, is a cliché too far. And among its own well-kept secrets , only now coming to light, is the fact that it is home to the biggest illegal toxic rubbish dump in Italy, and very probably in the whole of Europe.

In a narrow, densely wooded valley known as Gola dei Tre Monti (Throat of the Three Mountains), sandwiched between two national parks, forest wardens have uncovered an area covering four hectares packed with chemical waste to a depth of seven metres. They believe it contains a total of 240,000 tons of hazardous waste. Mafia gangs are known to make a killing by driving hazardous waste from northern Italian factories to wilderness areas in the south and dumping it there. But the culprit is believed to be closer at hand: a chemical plant in the nearby town of Bussi sul Tirino, which was set up to manufacture chlorine in 1902.

According to an investigation in L'Espresso, the weekly news magazine, the dump was the destination of waste from the Bussi plant between the 1960s and the 1990s with the knowledge of workers there.

The magazine claims: "There were those at Bussi who knew about the lorries that left late in the evening, loaded up with toxic waste. The drivers said that they were taking it to Germany, but the next morning they were back at the plant again, empty and ready to load up." Analysis of samples taken from the dump reveals a wide spectrum of toxic chemicals, including chloroform and mercury.

The region is now confronted with the challenge of what to do about the dump. Taking the stuff by lorry to Germany and dumping it in worked-out salt mines is said to be prohibitively expensive; encasing the whole dump in concrete, another suggestion, would not prevent further contamination.

Then there is the challenge of nailing the people to blame. Patrizia Fantilli, a legal expert with WWF, said:"Italy's laws on ecological crime are too weak."

But today the Environment minister, Alfonso Pecoraro Scanio, who is also the leader of the Green party, is expected to unveil a tough new law threatening polluters with prison and stiff fines. "If he can't get the law through, no one can," said Ms Fantilli.