Despite walking for three days, we’ve seen no one. Not a single hiker, dog walker or shepherd. Instead, golden eagles have circled lazily overhead, stags have boldly held our gaze, and rare blue butterflies have flitted around our booted feet. The silence here is deep and dense, broken only by birdsong.

This is the Madonie national park, also known as the Sicilian Alps, home to many of the island’s highest mountains and rarest plants. It’s a landscape of 200 million-year-old rocks, rich in fossils. Of raptors and the tiniest of songbirds. Of wild boar, fallow deer and porcupines. Of cyclamen and crocuses. Of the largest holly trees on the planet, and of 65 varieties of orchid. A landscape that is void of tourists, ramblers and Sicilians. For anyone in search of wilderness, solitude and sunshine, I can’t think of a better place.

Summer here would be too hot to wander. Spring – when the lush green landscape is dotted with sweet peas and poppies, and villages come alive with religious festivals – and autumn, when we visit, with its pink prickly pears hanging from cacti and rutting stags, are the best times to explore.

The 40,000 hectare park was created in 1989, when its biodiversity and geological rarity were recognised by Unesco as possibly the richest in the Mediterranean. My partner and I are here to walk from its hinterland to its rim on the northern coast of Sicily, not far from the capital, Palermo. Our route follows a section of the newly restored 166km Via dei Frati (The Way of the Friars), a trail once used by itinerant friars, pilgrims, beggars, mystics and missionaries. We shall be walking about 90km of sharp ascents and descents over seven days, starting from the village of Gangi (with views of Etna on a clear day). And yes, a century back, some of the Madonie’s medieval hilltop-perching villages were infamous mafia strongholds – all of which makes for a landscape as rich in history as it is in flora and fauna. Today, these villages – depopulated, dusty, replete with romantically ruined castles-on-crags and ridiculously ornate churches – are where we sleep.

We booked our guesthouses – in Petralia Sottana, Gangi, Geraci Siculo, Castelbuono and Cefalù – in advance, but could have saved ourselves the effort as we were the only guests. Each day, we head out on quiet country lanes that gradually turn into cattle tracks and then into hidden, winding paths. Here, we must keep a careful eye on the yellow arrows and red-and-white stripes, daubed on rocks and trees, that indicate the Via dei Frati. As we climb, we leave behind the horned cattle, shaggy goats and timid ponies that roam the Madonie’s verdant pastures. Now, skittish deer and their fawns clatter over the scree that often replaces grassland. Raptors soar. We dip and dive, through steep beech forests, past monumental oak trees rumoured to be a thousand years old, around woodlands of wild pear, ash and juniper.

In these most remote locations, we often stumble across tiny deserted chapels – and wonder how they were built, and by whom. These were vital places of refuge for the friars who once followed these routes, seeking alms in exchange for work.

The Via dei Frati was rediscovered by a Sicilian psychotherapist called Santo Mazzarisi. After walking several well-known pilgrim routes and wondering why Sicily had no trail of its own, Mazzarisi began researching, and then restoring, this ancient path. In 2017, it opened to the public, starting at Caltanissetta in central Sicily and ending at Cefalù on the coast. In the past, pilgrims then crossed the sea from Messina before heading to Jerusalem, but today’s route has been designed as eight stages, each ending in a village where food, accommodation and, of course, a beautiful church can be found. For a true pilgrim experience, Mazzarisi suggests visiting during holy week – 13-20 April this year – when Caltanissetta hosts processions of life-size statues re-enacting the Resurrection.

We join the trail at Gangi because this is where it hits the Madonie mountains. The park contains none of the usual trappings of civilisation so, of necessity, we carry a daily picnic, prepared by our guesthouse, and eat our focaccia sandwiches on sun-warmed rocks. Having explored Gangi’s museum, which is chock-full of geological and archaeological treasures unearthed from the park, we walk 14km to Geraci Siculo. We are not walking at our normal pace – there’s too much to distract us. Instead, we pause regularly to note the birds (buzzards, firecrests, buntings, tits and yellow-feathered serins), to examine the curiously striated rocks that are everywhere, and to exclaim over the remarkably “biblical” scenery. We feel as though we’re inside a Renaissance painting: grazing goats, wooded valleys, divinely slanting light.

In Geraci Siculo, we are beckoned into a library by its wizened curator, who proceeds to unlock glass cabinets stacked with 15th-century religious manuscripts. We cannot understand what he is telling us, but the odour of dusty pews drifting from the pages adds to the peculiar sense of time travel.

We continue to hike, upwards, through clouds, to Petralia Sottana, where we spend an additional day climbing Monte San Salvatore, following the scuffed tracks of rootling boar, clambering over granite boulders, and getting pleasantly lost.

From Petralia Sottana, we amble 16km to our next accommodation, an agriturismo called Azienda Bergi, just outside Castelbuono – arriving so exhausted we can barely muster the energy to eat the obligatory four courses of Sicilian cuisine: caponata, pasta with sardines, grilled lamb and gelato made from the sap of neighbouring ash trees and known locally as manna or “white gold”.

Apart from a stooped white-haired man foraging for fungi, we meet no one on our walk until the fifth day, on a sunny morning, near a car park with a cafe. We’re heading to the region’s world famous giant holly trees, 20 metres high and thick with scarlet berries, when we hear voices, dogs barking, cars reversing. The sound is such an affront to our ears we pick up our pace, almost running to return to the unpeopled wilderness we’ve fallen in love with. Minutes later, we are happily alone again until we reach Castelbuono. A taxi is planned to take us to Gibilmanna for the final 9km descent into Cefalù on the Tyrrhenian Sea. Although the route becomes increasingly urban, we are mollified by repeated glimpses of sparkling ocean and the knowledge that Cefalù has not only beaches but a Unesco-listed Norman cathedral among its many treasures.

In the past, we have hiked all over Europe, but – thanks to the strenuous ascents and silent nights – never have we slept so well. And never have we felt so deliciously solitary. If crowds are your thing, this park and the pilgrim route just won’t do. But if you like a landscape all to yourself, or a terrain so rich in geological history and so abundant with rare plants, insects and birds that you’re forced to walk at an unfamiliarly slow pace, the Via dei Frati will surpass all expectations.

Annabel travelled independently. For information on the route, visit laviadeifrati.it. Inntravel offers self-guided walks, while Esplora runs guided walks in the Madonie mountains. Annabel Abbs is the author of several books on walking, most recently The Walking Cure, published by Bloomsbury for £14.99 under the name Annabel Streets. To support the Guardian and Observer, order your copy for £13.49 from guardianbookshop.com