A 5,000 year-old underground city thought to be the largest in the world has been discovered in central Turkey.

The subterranean settlement was discovered in the Nevşehir province of Turkey’s Central Anatolia region, in the historical area of Cappadocia.

Cappadocia is famous in archaeological circles for its large number of underground settlement.

But the site, located around the Nevşehir hill fort near the city of Kayseri, appears to dwarf all other finds to date.

Hasan Ünver, the mayor of the city on those outskirts the discovery was found, said other underground cities were nothing more than a “kitchen” compared to the newly uncovered settlement.

Mehmet Ergün Turan, the head of Turkey’s housing development administration, said the discovery was made during the groundwork for a housing project meant to develop the area.

Derinkuyu underground city, to the south of Nevşehir city (Creative Commons / Nevit Dilmen)

“It is not a known underground city. Tunnel passages of seven kilometers are being discussed. We stopped the construction we were planning to do on these areas when an underground city was discovered,” Mr Turan told Turkish publication Hurriyet Daily News.

The agency has already spent 90 million Turkish liras (£25m) on the development project, but the organisation’s head said he did not see the money spent as a loss due to the magnitude of the historical discovery.

The upper reaches of the city were first spotted last year but it was not until now that the size of the discovery became apparent. The organisation has so far taken 44 historical objects under preservation from the site.

Cappadocia's characteristic volcanic rock landscape lends itself to underground cities (Creative Commons / Peretz Partensky)

The area has been officially registered with Turkey’s Cultural and Natural Heritage Preservation Board and no further building work will be done.

The Cappadocia region, once a Roman province, is fertile ground for underground cities because of its soft volcanic rock which is easy to carve.

Nevşehir province’s most renown underground settlement is Derinkuyu, a multi-level city large enough to house many thousands of people and their livestock. It lies within an hour’s drive south of the new discovery.

The town of Nevşehir, on whose outskirts the new underground city was discovered (Creative Commons / Georges Jansoone JoJan)

Derinkuyu, believed to date to the 8th century BC, was most recently inhabited by Christians until 1923 when they were expelled during a population exchange with Greece.