Pietra di Bismantova

Pietra di Bismantova is an isolated tabletop massif in the Reggio Emilia Apennines of northern Italy, a narrow plateau roughly a kilometer long and 240 meters wide, ringed by cliffs some 300 meters high and reaching an elevation of 1,047 meters. It is built from yellowish calcarenite over a marl base, both laid down as sediment on the floor of a warm Miocene sea that once covered the area, later uplifted and left standing as a steep-sided monadnock once the softer surrounding rock wore away. The formation, believed by many scholars to have inspired a passage in Dante's Purgatorio, sits within the Tuscan-Emilian Apennine National Park.