On the northern slope of the Ligurian Appennines, in the valley of the Bormida di Spigno, the commune includes the protected area containing the famous “mushroom” of Piana Crixia, the result of an unusual process of erosion. Perhaps of Roman origin, it was devastated by the Saracens at the beginning of the tenth century. In the middle of the twelfth century it became a possession of the Del Carretto, who built a castle there. In 1337 it was ceded by the marchese di Saluzzo to the Scarampi of Asti and was annexed to the kingdom of Sardinia in 1735. The parish church, dedicated to the martyrs St. Eugenius, St. Victor and St. Corona, was built in the baroque manner between 1715 and 1765. The ruins of a castle in the hamlet of Borgio are of medieval origin. Another was built near it in a pseudo-medieval style in the nineteenth century. The houses are surrounded by dense natural vegetation, as well as by cultivated fields and vineyards.