Growing passion: Ancient secret behind Italian farm that produces some of nation's finest olive oil

When Stefano Fassone decided to excavate a tunnel full of dirt and dung on his farm near Mompeo, he got far more than he'd bargained for. After 11 months of digging, he'd discovered a 2,000-year-old olive-oil vault amid a labyrinth of underground rooms in a Roman farmhouse untouched for centuries, and also found true love with Elizabeth, a volunteer helping on the project. It's difficult to know which of the discoveries he's more passionate about.

Olives are a huge passion in this rustic corner of Italy, just 50km north of Rome. In early November, the hillsides are buzzing. Neat, silvery olive groves, deserted for most of the year, are full of people. Predominantly, these are ladies in old-fashioned floral pinafores climbing up ladders with green nets spread out below like carpets to catch the season's crop.

Over in the village press, the men wait for their olives to be cleaned and crushed and to emerge from the taps, sometimes like liquid gold or sometimes a cloudy, mossy green. It's the smell of the press that hits you first: grassy and pungent, like the first lawn-mowing of spring but much more intense.

As the first "extra virgin" of the season pours out, the eager farmers tear up some bread and dip into the oil, savouring its peppery, spicy freshness. It's a scene that is played out all over Italy in the autumn, most famously in Tuscany – a region now synonymous with the olive-oil industry. But I'm in Sabina, a beautiful yet surprisingly little-known area of rolling hills and pretty medieval hilltop villages that dot the landscape like freckles.

Largely ignored by the guidebooks, this region is classified as a DOP area, (denominazione d'origine protetta or Protected Denomination of Origin). It produces some of the country's finest olive oil and, as Stefano proved in his own back yard, is home to an olive-oil heritage going back millennia.

Five years since his excavations ended, Stefano's land now forms the region of Lazio's newest Natural Monument, Le Gole del Farfa. He specifically requested this designation to ensure the villa Romana he'd found would be protected. "My mother's not too pleased, because it means I can't build on the land," he tells me with a wry smile. "But I wanted this to be here for everybody."

Stefano and Elizabeth now live in the medieval shepherd's cottage that lies above the Roman ruins. Among olive trees, some piles of stones, and the couple's home, little remains of the original farmhouse above ground. Stefano tries to outline the building's former location to me, so huge it covered almost one hectare, but my imagination struggles. Then he rushes ahead like an excited child wanting to share his secrets and leads us to a subterranean tunnel so perfectly intact that my imagination becomes redundant.

This cryptoporticus, to give it its Latin name, leads to a long archway that Stefano has lit with candles in small alcoves to guide the way. The gentle candlelight reveals a pure white calcified ceiling with tiny stalactites dangling from it. While I'm standing in amazement at how perfect the structure is, Stefano rushes ahead again. "Come on," he urges impatiently. "I have an even better surprise."

He takes me next door, to a room where the sun streams in from a high, arched window above three troughs, each measuring about one metre square. "This is the best part," he says proudly.

Stefano had been convinced this farm was used for olive oil production but, despite excavating tons of animal waste and human detritus, had unearthed little evidence. Finally giving up, disappointed and disheartened, he kicked a "stupid, stubborn" stone as he left the room – only to reveal the rim of the first trough and potential proof of his theory. Even as he tells his story, he is jumping up and down, reliving his moment of elation, and my spine starts to tingle – I'd never thought excavating manure could be so exciting.

Believing he'd found evidence of a Roman twin-trough system for storing oil (a structile gemellar), he began digging for the second one. He found not two but three troughs. Stefano explains how the oil would have poured into the troughs through a hole in the ceiling above, where donkeys or slaves turned the olive mill. It was then separated from the water by ladling it into the third trough, a system dating back possibly as far as 3BC and confirming the presence of olive oil production here some 2,000 years ago.

Today, he still picks the 900 olive trees to produce extra-virgin oil with the help of volunteers from all over the world. After a crash course in olive-picking from Stefano, they work six hours a day for free board and lodging. But you don't have to work to stay here: Le Mole sul Farfa is an organic agriturismo on the grounds of Le Gole with a swimming pool, a stunning vegetarian restaurant and bags of rustic charm.

Another aspect of Stefano's olive venture is guiding visitors on walks around Le Gole. He escorts them along ancient Roman trails, taking in a dramatic 2.5km gorge of the Farfa River, the ruins of a medieval watermill and aqueduct, and his villa Romana. He also introduces people to his favourite olive trees; some of these probably date back to the time of the olive-oil troughs and produce now rare varieties of Sabina olives.

Stefano's groves have never seen a tractor: the steepness of the hillsides and the rocky terrain render such modern farming tools useless. Instead, he employs traditional methods to keep the grasses low: two donkeys, 20 sheep and 12 goats looked after by a 77-year-old shepherd named Uomo (which simply means "man" in Italian).

As we walk, the Sabine Hills are spread out all around us, with precarious-looking villages and fortresses perched on peaks above patchwork slopes of olive groves and dense, green oak woodlands. "At sunset, I take walkers inside the villa. The reflection of the sun lights up the archway, turning it bright red and then they come out here by the olive trees to see the sun go down," he says.

Some 20km away, in the nearby town of Canneto, stands what is believed to be the biggest olive tree in Europe. In its size (a 7m circumference) and shape it resembles an English oak more than an olive tree. It yields a tonne of olives each year. I feel dwarfed standing beside its twisting, gnarly trunk. It's vast but somehow lacking in character compared to Stefano's trees.

For a living, breathing slice of Sabina olive history, you need to spend time at Le Gole del Farfa. "It's a special place" Elizabeth tells me as we talk about the timeless atmosphere of the villa Romana. No wonder they fell in love with it.

Branching out

Getting there

Rome's Fiumicino airport is served by British Airways (0844 493 0787; ba.com); Alitalia (0871 424 1424; alitalia.com) and Bmibaby (0905 828 2828; bmibaby.com). Ryanair (0871 246 0000; ryanair.com) and easyJet (0905 821 0905; easyjet.com) fly into the city's Ciampino airport. By rail, the best connections from the UK are via Paris.

Staying there

Le Gole del Farfa Natural Monument and Agriturismo Le Mole sul Farfa (00 39 328 460 3412; fiumefarfa.eu). Doubles start at €60 including breakfast. Four-course restaurant meals cost €24 per person. Walking tours cost €7 per person for one-hour walks around the villa Romana and olive trees or around the medieval mill, aqueduct and gorge, or €15 for a four-hour walk combining both. To volunteer for a work camp, contact Concordia (concordia-iye.org.uk). A registration fee of £150 applies and volunteers have to pay for their own travel to Italy.

Visiting there

Museo dell'Olio della Sabina (00 39 0765 32091; museolio@yahoo.it). Open Fridays 3pm-8pm; Saturdays 10am-8pm; Sundays and holidays 10am-1.30pm and 2.30pm-8pm. Admission €5.

More information

Italian State Tourist Board: 020 7408 1254; italiantouristboard.co.uk

Branching out

Sabina is slowly waking up to the fact that it can combine its olive heritage with the demand for holidays in the area. There are now various options for olive lovers coming to the area, with differing degrees of activity:

Terra Sabina

This new agriturismo near the bustling market town of Poggio Mirteto offers a real farm experience where guests can help pick the olives, visit the press and take home their own oil. The farm also grows all its own vegetables and guests can help with these too, learning to cook in a traditional Italian way.

Terra Sabina (00 39 0765 446037; terrasabina.it). Doubles start at €140, half board. Open all year.

Villa Vallerosa

Self-catering apartments in the grounds of a stunning 18th-century villa in the medieval village of Selci. The owner, Luciana, appreciates that not everyone will want to spend all their holiday out in the groves and offers a four-day olive programme that includes a day picking olives with local farmers and a visit to Le Gole del Farfa.

Villa Vallerosa (00 39 0765 607565; villavallerosa.it).

Costs €350 per person for three nights' full board – apart from dinner on the third night – including tours to the olive museum, Le Gole del Farfa (nearby bridge pictured), a visit to the olive press, and olive oil tastings.

La Torretta

An atmospheric 15th-century palazzetto (town house) in the heart of Casperia's medieval centre, which offers day-long tasting tours of prize-winning olive oil, plus cookery lessons.

La Torretta (00 39 0765 63202; latorrettabandb.com). Doubles from €80, including breakfast.

Borgo Paraelios

For pure indulgence, this five-star hotel near the village of Poggio Catino is the best in the area. If you want to combine the local food and oil with fine dining, try the Sabina menu (€25) in its restaurant, La Casina nel Parco.

Borgo Paraelios (00 39 0765 26267; borgoparaelios.it). Doubles from €330, including breakfast.

La Vecchia Quercia

A restaurant with rooms just outside the medieval village of Selci, which offers a more rustic alternative to Borgo Paraelios. Pino, the owner, serves up 14 delicious antipasti dishes cooked with his own oil, followed by dishes such as wild boar on toast.

La Vecchia Quercia (00 39 0765 519207; lavecchiaquercia.net). Doubles from €80, including breakfast.

Sabina Si

If you want to find your own way around the hills, groves and olive presses – and cook in the comfort of your own kitchen – this agency has some beautifully situated self-catering villas and apartments around Sabina (00 39 0765 607565; sabinasi.it).