Police in Rome have sniffed out a cannabis factory in an abandoned metro tunnel built during the rule of Fascist leader Benito Mussolini, in the 1930s.
Officers reportedly stumbled across the factory after smelling the pungent crop near an entrance, not far from the Italian central bank.
The tunnel, just over half a mile (1km) long, was also being used to cultivate mushrooms.
But behind a makeshift wall, police discovered rows of marijuana plants.
Video released by Italy’s financial police show an underground greenhouse with thriving marijuana plants lit by halogen lights, and irrigated via a system of underground cisterns.
There were also special chambers for drying and processing the crop.
Italy’s financial police said the find was among their biggest ever seizures of cannabis – a total of 340kg of the drug with an estimated street value of 3m euros (£2.3m; $3.7m).
Some 900 plants were being cultivated across half a hectare in the tunnel.
The discovery of the illegal factory, some seven metres below the city, took place near in south-eastern Rome on Saturday.
The farm’s owner, a man in his fifties, has been arrested.
“We were carrying out checks when, from below – where we later uncovered the entrance to the tunnel – we smelled the incredibly strong and unmistakable smell of marijuana,” police chief Stefano Corsi said.
Police suspect that the farm may have been part of a larger operation involving more than a dozen people and supplying the drug across the country.