The Appian Way runs south from Rome across the Pontine Marshes, and at Terracina it meets a wall of rock. The Romans did not go round it. In the early second century AD the emperor Trajan had a vast cutting made through the cliff, leaving a sheer wall about thirty-five metres high, and carved numbers into the rock face at intervals of ten Roman feet so that the labourers could track their progress. The marks are still visible, and standing at the bottom looking up gives a sense of the scale of Roman road engineering. The place is called Pisco Montano, and the road still runs through it.
Terracina, the Roman Anxur, is a town of thirty-one thousand people on the coast between Rome and Naples, with a long sandy beach below and an old town built on a hillside. On top of the hill stand the remains of a huge temple of Jupiter, built on terraces of arches and arcades in the first century BC, and from there the view takes in the sea, the Circeo promontory and, on a clear day, the islands of Ponza. The cathedral, built into a Roman temple, has a pavement of old stones and a pulpit with mosaics.
Farther inland, at the pass of Lautulae, the Romans fought and lost a battle to the Samnites in 315 BC, one of the early reversals in the long wars for control of central Italy. The ground has changed, but the narrow strip between mountain and marsh still shapes the line of the roads.
The ride here is a good one. The coast road to Sperlonga and Gaeta is a series of bends above the sea, with cliffs, caves and little beaches below. At Sperlonga, the grotto of the emperor Tiberius, where a banquet was held in the first century and the roof collapsed, has a museum of the sculptures found there. Inland, the Monti Ausoni offer quiet roads through olive groves and villages. In summer the coast is crowded, and traffic is heavy at weekends, so go early or come in spring and autumn.
Terracina has fuel and plenty of seafood restaurants. Try spaghetti with clams or a fry of small fish. Late spring is lovely, with warm days and a clear sea.