It was the first modern road in the world, shooting like an arrow from the Porta Capena in Rome's city walls all the way to Brindisi on the Adriatic coast, more than 500km (300 miles) away. Today the Via Appia is at the centre of a regional park, protected by the city of Rome and Unesco as the patrimony of all humanity. At least that is the theory. But although it has become a popular weekend draw for Romans and visitors, the Via Appia is in trouble. Twenty years ago the regional government passed a law to protect it, but despite its Unesco listing it is fighting off colonisation by property speculators gambling on the likelihood that Silvio Berlusconi will win Italy's upcoming election and his government will, like his two previous ones, enact a condono or amnesty on illegal building. Sixteen illegally built villas have been condemned and demolished in the park in the past five years, but many have survived. And the way the amnesty law works poses a vivid threat to the park's integrity. During the last amnesty enacted by Mr Berlusconi, in 2003, 90,000 applications were made for the regularisation of illegal buildings in Rome alone. But officials given the task of vetting them believe one-third referred to structures as yet unbuilt, allowing their authors to go ahead and build them, secure in the knowledge that they could not be stopped. It was the fourth such amnesty in as many decades. Work began on the Via Appia in 312BC and by 191 it had reached its objective: practically dead straight the whole way, built using huge stones closely set over a stratum of crushed stone to assure good drainage, and wide enough to allow marching legions to pass each other. The building of the Via Appia, the "queen of roads" as it was known, was the key step towards Roman domination of the eastern Mediterranean. Many centuries of benign neglect destroyed its efficiency but enhanced the charm of the sections that remained intact. Today the ancient surface, which looks as if built by giants, is buckled and broken, making it a severe test for the mountain bikes that bounce along it at weekends. But the road is lined with high umbrella pine trees, ruined castles and villas, and funerary monuments, many of great antiquity. On a sunny day in spring it is a place of magic. It was first recognised as an important historical legacy by Napoleon, but preserving it for Romans to enjoy in the future has been an uphill struggle. The campaign to preserve it began in earnest in the 1960s, launched by a journalist called Antonio Cederna, who dedicated his career to the task. When he began his campaign, only a thin strip on either side of the road was protected. The then mayor of Rome took up the battle in 1979, calling for the Appia to be part of a great archaeological park covering much of Rome. Nine years later the necessary legislation was passed. But by then much of the Appia had been taken over by developers: more than 90 per cent is in private hands, and it has become one of the poshest residential areas in the capital. Under pressure to do more to bring the park to realisation, the Culture Ministry buys up properties within the park's area when they come on the market. But funds are severely limited. Meanwhile, owners of properties within the park quietly move the goalposts, converting old tanks into swimming pools without permits, tacking restaurants on to facilities licensed to sell garden plants, nibbling away at the park's integrity. One section near the ancient Roman wall is now a favourite rat-run for traffic racing towards Rome.