The Onferno Nature Reserve is located in the Province of Rimini, in the calm hills of the hinterland of the Valconca, bordering the Montefeltro, in view of the Adriatic coast and the Republic of San Marino. Characterized by quiet and total immersion in nature, it offers serenity and well-being.
The karstic complex of the Onferno Caves, known since the nineteenth century, is considered among the most important in Italy with regard to the caves in the gypsum.
Two small streams descend from the clayey slopes of Monte Croce and after reaching the chalky cliff of Onferno they become one and they begin to flow underground for a short stretch. 
The waters resurface a little further downstream, inside a densely wooded gorge. The cave develops along the entire hypogeum of the watercourse at the base of the large and unique chalky stone on which the "Castrum Inferni" once stood.

Onferno or Inferno? The first is the current name given to the village in 1810 by the Bishop of Rimini, who did not like to have, in his territory, a village whose name had such a clear reference to demons and underworld; the second is the ancient one (from the Latin infernum: low and dark place) given by the inhabitants of the place, who believed that the entrance to the cave was nothing else than the entrance to Hell. Imagine a very wild place, the ravines, the woods and the 'fumes' : the population of the place was sure to live in a 'diabolical' environment. 
Among the main activities there were the extraction and baking of gypsum, which lasted until the fifties of the last century. On the top of the cliff, where the castle once stood, a small village remains in a beautiful panoramic position on the reserve and the surrounding territories: to the north is the unmistakable profile of San Marino, further east from the sea.

The Cave of Onferno was explored for the first time in 1916 by Lodovico Quarina, who described its morphologies and concretions. In the first part, along the stream, you can walk through tunnels with vertical walls shaped by water. In the next stretch we can reach fossile enviroments where some rooms  expanded due to collapsing phenomena. In the Quarina hall the vault is enlivened by curious conical structures called “mammelloni”. Here the climate is warmer and drier than in the galleries where the water flows. The cave has a development of about 400 meters and one of its peculiarities is the presence of bat colonies. In fact it hosts the most important colony of bats in the Region, more than 8000 and seven different species. The territory of the Reserve Is very particular also as regards the flora that grows under the influence of the caves themselves which have a constant temperature of 12/13 degrees throughout the year .The headquarters of the Nature Reserve are in the ancient parish church of Santa Colomba, now restored and used as a visitors center and naturalistic museum.
Rates of entry include entrance to the Oriented Nature Reserve, Visitors' Centre and Museum.
Many AGTI caves have reopened or are about to reopen, in strict compliance with the rules due to the health emergency. To find out times, how to access and book visits, you must contact the caves directly. Find the references on www.grotteturistiche.it