Welcome to Gúdar Javalambre. This remote county in eastern Spain covers 2,350 sq km but contains only 24 villages and fewer than 9,000 inhabitants. It belongs to Teruel, one of the three provinces of Aragón and a region best known in Spain for Teruel Existe (“Teruel exists”), a citizens’ campaign launched in 2000 to call for more investment and to fight depopulation. This land of massive skies and tiny population densities — as low as 3.7 people per square kilometre — reminds you how vast and empty much of Spain still is, away from the boisterous cities and teeming coasts.

Gúdar Javalambre’s efforts to forge a future are a fine example of the adage that necessity is the mother of invention. The climate here can be harsh and the soil is too poor and dry for arable agriculture. Communications are not all they could be. Yet the county is doing what it can to get ahead. As interest grows in lesser-known parts of Spain’s unspoilt interior, visitors are increasingly being drawn to Gúdar Javalambre’s wild natural beauty and gourmet products, such as its superb air-dried ham. There is good infrastructure at ski resorts such as Valdelinares and Javalambre, and the new A23 motorway has brought Valencia airport within a 90-minute drive. The absence of light pollution in the skies — plus the news that Galáctica, an observatory/museum of global importance, is scheduled to open here this year — has led to the rise of “astro-tourism” in the county, with guided starlight walks.

But the most remarkable draw is the truffle. Until the 1960s the sought-after fungus was little known in Spain and European truffle culture was dominated by the French and Italians. But since the discovery that the “black diamond” could be grown in the meagre soil of Teruel, the province has experienced a production boom. Planting began in the 1980s and some 6,500 hectares of truffle-producing carrasca oak trees are now under cultivation.

I have come to the county for a long weekend at La Trufa Negra, a hotel whose pioneering “truffle tourism” package includes a truffle-hunting expedition with dogs, a truffly tasting-menu and truffle-based therapies in the hotel spa. Now in its fourth year, “trufiturismo” at the hotel has grown to the point where it brings in 60 or more customers on any given Saturday, in a season that lasts from November until March.

The Pérezes have long been one of Mora’s more prominent families. Emilio, the patriarch, was a farmer before he bought the village’s first lorry in 1963 and founded a transport company which became the cornerstone of his business empire. The new generation are his granddaughter Alexandra, 26, who runs the hotel, and her sister Alba, 20, a student of agronomy who, together with their father Miguel, looks after La Masía El Olmo.

La Trufa Negra is a shrine to its namesake. Black truffles from the family farm are a mainstay of Melanosporum, the hotel restaurant where chef Victor Pérez (no relation) showcases them in dishes ranging from the luxuriously plain (olive oil-macerated carpaccio of truffle on toast) to the plainly luxurious (salad of truffle shavings and duck ham with peach and curry vinaigrette). Truffles are sold in the lobby, fresh, steeped in brandy, and infused in cheese and longaniza sausage. They also feature on the menu at the hotel spa, which claims its truffle-derived cocktail of vitamins, minerals and polyphenols works as a “natural Botox” for the skin.

On a rapidly darkening Friday afternoon I make the short drive to Mora’s twin village, Rubielos de Mora. I have been enchanted by Mora’s 14th-century church of Santa Maria la Mayor, a glorious Gothic barn, and the village’s mighty castle in dust-coloured stone, which would not look out of place in Game of Thrones. But Rubielos de Mora is, if anything, even more impressive architecturally. The grandeur of its 27 historic mansions gives an idea of the village’s once-enormous wealth, derived from the wool trade, which reached its peak in the 16th century.

The truffle, Gúdar Javalambre’s newest hope for potential riches, is less in evidence here, though if the menus in the tapas bars and restaurants are anything to go by, it is gradually finding a place in the cuisine. That evening at Los Leones, a fine little palace-hotel, owner Manuel Górriz serves me an aged sirloin steak adorned with thin truffle slices bestowing a pungent aroma on the simply cooked meat.

Back in Mora, Saturday dawns bright and bracing. I take my place along with eight other “truffle tourists” — they include a chef, a cherry farmer and a food-loving family from Bilbao — in the hotel screening room where Alexandra Pérez offers us an introductory course in thetrufa as species, crop and ingredient. Thanks to her explanations I learn the taxonomy of the truffle family and to easily distinguish Tuber magnatum, the renowned wild truffle of Piedmont, from Tuber aestivum, the milder-flavoured summer truffle, andTuber melanosporum, the black winter truffle traditionally associated with Périgord in southwest France but now cultivated here on such a scale that local producers claim Teruel accounts for a fifth of the global crop.