Still from a video by the Guardia di Finanza
Italian authorities found an illegal marijuana farm

Italian authorities have found a marijuana farm in a tunnel that late dictator Benito Mussolini planned as part of Rome's subway system.

Italy's tax police officers made the discovery after they detected the smell of dried marijuana emanating from the abandoned tunnel.

The tunnel was rented out for growing mushrooms but behind a fake wall officers found a sophisticated cultivation system, which included irrigation and artificial lights to help the plants grow.

Up to 340kg (748lbs) of marijuana was found in the farm, with a street value of €3m.

The tunnel was divided into sections, with a hothouse and a cutting and packing room.

A number of vacuum-sealed bags full of marijuana ready for sale was also found.

The farm also had an alarm system, La Republica Roma reported.

The tunnel was excavated and partially built in the 1930s as Mussolini had hoped to expand the city's subway system.