Standing on the top of the huge fortress, looking over the rolling landscape, it’s easy to see why Nepi was a prized possession for Roman emperors, medieval popes and Renaissance dynasties. Defended on two sides by river channels and with a commanding position over rich agricultural land and abundant water springs, the town, less than an hour north of Rome, has been a witness and a contributor to history for over two millennia.

Much of that history has been marked by intrigue, violence and war. Most famously, Nepi was ruled by the 15th-century Spanish cardinal Rodrigo Borgia, who gave it to his daughter Lucrezia after he became Pope Alexander VI. Lucrezia stayed at the fortress (today known as the Borgia Castle) following the murder of her second husband in 1500. These days, things are a lot more laid-back. I’m sitting outside the Bar Centrale in the town’s elegant Piazza del Comune, facing the imposing town hall, built on the orders of the Farnese family after they took up residence here in the mid-1500s. With me is Paolo Paoletti, who has just been elected for a second term as Nepi’s councillor responsible for culture and tourism. While I sip an espresso and tuck into a cream-filled pastry, Paolo tells me about his plans to develop tourism here and across the Tuscia region.

Once the land of the Etruscans, Tuscia roughly corresponds to what is now northern Lazio. Nepi lies at its heart, about 31 miles (50km) from the capital. Paolo’s ambition is to connect it with other local towns to create a tourism network that will enable visitors to experience Tuscia’s historical, cultural and natural attractions. The development of a web portal is a first step. This will position Nepi as the hub of what Paolo laughingly calls “Tuscialand”. But he is also conscious of the need to protect Tuscia’s relaxed, traditional way of life from waves of invasive tourism that have recently overwhelmed many Italian towns and cities. Nepi’s 50-plus B&Bs and short-stay apartments are small-scale affairs run by local people, and Paolo wants them to stay that way. “It’s important to get the understanding and support of the community,” he says, “so that visitors feel welcome but residents don’t feel threatened.”

I’m staying in a palatial 18th-century apartment, conveniently located above the Bar Centrale. Owners Alessia and Francesco already run the Loft Delle Scalette on the other side of the piazza, and they are planning to offer this three-bedroomed space for tourist accommodation early next year.

After a second cream pastry, Paolo whisks me off to the neighbouring town of Castel Sant’Elia. We make the short journey by car, but we could easily have walked the two miles. Across Tuscia there are paths, trails and ancient Roman roads ideal for walking, trekking and cycling. With plenty of sunshine and temperatures reaching a comfortable 20C, early autumn is the perfect time to explore the region’s impressive landscape and to spot wildlife such as porcupines, wild boars, peregrine falcons and black kites.

Nepi itself is edged on two sides by a deep gorge formed by river channels running through the volcanic rock of the Cimini and Sabatini Hills. Beyond, the expansive and undulating countryside is carpeted with fields and woods, and criss-crossed with streams and waterfalls.

One of the trails takes you through the Suppentonia valley to Castel Sant’Elia’s 11th-century basilica, where we meet Paolo’s opposite number, councillor Cecilia Paolucci. She points out a fresco filled with scenes from the Apocalypse of Saint John. The saint is associated with the winter solstice, and every year at dawn on 21 or 22 December sunlight enters each of the high windows on the left of the basilica, creating a mystical illumination.

A different kind of wonder is on offer at the Villa Farnese at Caprarola, about 12 miles to the south. Towering over the town and the surrounding volcanic hills, the villa was built by the Farneses as a statement of their wealth and power. The interiors are covered with frescos glorifying the dynasty, while the sprawling gardens include a monumental cascade, an eerie hedge-and-statue quadrangle and a wooded secret garden.

Back in Nepi, it’s time to explore the ancient catacombs. Like Rome’s more famous underground chambers, these were originally scooped out of tufa rock for burials rather than for secret religious meetings. The multistorey niches once housed around 1,000 corpses. A few bones still remain, together with some faded paintings and black crosses marked on the walls with the smoke of oil lamps.

From there it’s a short walk to the baroque splendour of Nepi’s cathedral, where we discover the town’s English connection. A marble plaque in Latin records the presence in the cathedral of what are claimed to be a pair of relics – long since lost – of Saint Thomas Becket of Canterbury. Nearby is a portrait of Saint Romanus, who, along with Ptolemy, is the town’s patron saint. But Romanus’s face is that of Reginald Pole, “Bloody” Mary Tudor’s distant cousin and archbishop of Canterbury during her attempted Catholic reconversion of England. In Henry VIII’s reign (in 1532) Pole went into exile in Rome, where he was made a cardinal and given the governorship of Bagnoregio, the so-called “dying town” perched precariously on top of an eroding hill.

The English have been coming here for centuries: first, as pilgrims on their way to Rome; then as grand tourists. JMW Turner spent time in Nepi in 1819 and again in 1828. He sketched and painted several views (now in the Tate Gallery in London) of the cathedral, the castle, the 18th-century aqueduct and the nearby waterfall. He likely sampled Nepi’s famous mineral water, which is sourced and bottled here. Maybe the water supply has something to do with Tuscia’s reputation for producing musical talent. Baroque composer Domenico Massenzio was born in Ronciglione, while his contemporary Alessandro Stradella grew up in Nepi. Both are celebrated at an annual music festival (which runs in September).

It’s time for lunch, so Paolo takes me to La Corte, a smart but relaxed restaurant directly opposite the castle. Chef Gabriele Zampaletta is on hand to advise and prepare a range of Tuscian dishes using seasonal produce from the local area. If the typically rustic tagliere board of meats and cheeses (including pecorino romano made from sheep’s milk) doesn’t appeal, then try the panzanella – bread pieces soaked in sulphate water (from Nepi, of course), mixed with tomatoes, herbs, olive oil and slices of Nepi’s homegrown variety of flat, sweet onion. It’s authentic, unpretentious and moreish – much like this undiscovered part of Italy.

The trip was provided by the Comune di Nepi. The Loft Delle Scalette apartment and annexe costs around €90 (£75) a night