The Spungone, from the dialect spugnò or spungò for its “spongy” aspect, is a particular type of calcareous sandstone rock that shapes the surrounding hills and that influences the geology of the territory and the local agriculture, in particular the wine and oil production.

The Spungone is made up of a coarse mixture of seashells held together by a calcareous cement. It originates from marine deposits (of a relatively low sea) settled during the Middle Pliocene, about 3 million years ago, on raised areas that constituted the Romagna of that time.

Currently the Spungone forms a sort of rocky ridge that makes up the hills. The most evident outcrops can be observed in the points where the hills are crossed by the course of the rivers, like for example, at the summit of the Bertinoro hill (under the fortress).