The hypogeum oil mill, frantoio, was built by enlarging an already existing underground cave. From the stable on the grounds of the Masseria, a staircase with a barrel vault leads down to a big area surrounded by a series of niches specifically dedicated for different uses in the oil processing. There is also a kitchen with a fireplace, fucagna, and a sleeping area: the workers arrived at the Masseria in November, when the harvest of the olives started and lived in the oil mill until April.

Covering an area of 400 square meters in total, the whole mill is illuminated by several skylights, some of them also used to throw down the olives. The temperature inside is around 20°C from October to April, which provided favorable conditions for the manufacture of quality olive oil.