The Santerno valley climbs south from Imola into the Apennines toward Tuscany, and about fifteen kilometres up, the river cuts through a ridge of shining grey-white rock. This is the western end of the Vena del Gesso Romagnola, the gypsum vein that runs across this part of Romagna, and Monte Penzola rises above the village of Borgo Tossignano, with Fontanelice and Casalfiumanese nearby.
Gypsum, a soft mineral that forms in evaporating seas, creates its own kind of landscape: sinkholes, caves, cliffs that glitter with crystals, and a flora adapted to dry, alkaline soils. The Vena del Gesso was laid down about six million years ago, when the Mediterranean partially dried up, and it is now a regional park and part of the UNESCO site for the evaporitic karst of the northern Apennines. Near Borgo Tossignano, the rock has been quarried, and the cliff faces show the layers of crystals clearly. The village of Tossignano, perched on the ridge above the valley, has a fine view.
Imola, down on the plain, is home to the Autodromo Enzo e Dino Ferrari, the racing circuit where Formula One and motorcycle races have long been held. It is also where Ayrton Senna died in 1994, and there is a memorial to him at the Tamburello corner. Romagna is motor-racing country, home to many famous motorcycle racers, and the passion for bikes is palpable.
The riding up the Santerno valley is excellent. The SP610 Montanara road follows the river through Borgo Tossignano and Fontanelice toward Castel del Rio and the Tuscan border, with a good sequence of bends and pleasant views. From Castel del Rio, with its medieval humpback bridge, the roads over the hills toward the Senio and Sillaro valleys are twistier and quieter. Surfaces are generally good, and traffic moderate, with more bikes at weekends.
Castel San Pietro Terme, about thirteen kilometres away, is the nearest town of size, and Borgo Tossignano has fuel and bars. Local food includes the cappelletti and tagliatelle of Romagna and, in autumn, the chestnuts and mushrooms of the Apennines. Spring and autumn are the best seasons; summer can be hot and hazy in the valleys.