The geology of Bologna

Geology isn’t just found in books or museums. You can actually touch it.

It emerges in the milky reflections of selenite, in the red of the bricks, in the stones of the towers and in the subsoil of Bologna, extending out to the outskirts of the city where the landscape reveals its living matter.

Read this guide to Bologna’s geological sites and discover places where you can admire the materials and walk along the roughest paths amongst gypsum, selenite and other historic rocks.

Salaborsa and Piazza Maggiore

The ideal spot is Sala Borsa, in Piazza del Nettuno. Beneath the glass floor, you can see the archaeological excavations of ancient Bononia: Roman remains, medieval foundations, traces of Ulisse Aldrovandi’s Botanical Garden and wells linked to the groundwater.

Here, Bologna’s subsoil becomes a first mental map: clay and silt in the historic centre, sand and gravel towards the areas marked by the Reno and Savena rivers.

A visit to the Sala Borsa Excavations is possible for a donation during the times indicated on the official website. It is a short stop, perfect for embarking on a geological tour of Bologna without leaving the city centre.

From Sala Borsa, it is just a short walk to Piazza Maggiore. Here, Bologna’s geology shifts from sediments to architecture.

Terracotta and brick, born of clay, lend colour to palaces, porticoes and towers. They can be seen in Palazzo Re Enzo, Palazzo del Podestà and Palazzo d’Accursio. In the Sala d’Ercole of Palazzo d’Accursio, the fresco of the Madonna del Terremoto commemorates the earthquake of 1505: a historical detail that links Bologna to the seismic activity of the Apennines.

Torre Garisenda, Casa Conoscenti, Palazzo Davia Bargellini

Selenite is one of the key words for understanding Bologna’s geology. It is a variety of gypsum with a milky sheen, hence the name linked to Selene, the moon.

It can be seen in the Garisenda Tower, in the foundations of some towers and in the remains of the ancient walls. In Via San Vitale, the Serraglio di San Vitale preserves traces of the Cerchia dei Torresotti, built with terracotta and blocks of selenite.

Another worthwhile stop is Casa Conoscenti, in Via Manzoni, where blocks from the first ring of walls, known as the Cerchia di Selenite, are visible. It is a small, almost hidden passage, but a very clear one for those seeking rocks and monuments in Bologna without leaving the city centre.

From here, the route can head back towards Strada Maggiore. At Palazzo Davia Bargellini, the sandstone atlases face the street; a little further on, the portico of Santa Maria dei Servi features Istrian limestone, which arrived in Bologna in historical times thanks in part to the waterways of the Adriatic and the plain.

Geosites in Bologna: ideas for extending the route

Those wishing to go further can use the theme of geosites as the central theme of their journey.

And if you’d like to explore further, remember that the Emilia-Romagna Region provides information sheets on regional geosites, complete with descriptions, maps and scientific content.

A longer option is the Via dei Gessi e dei Calanchi, a 102-km route linking Bologna to Brisighella and Faenza. It is ideal for those who wish to transition from an urban itinerary to a multi-day trek through gypsum formations, ridges, valleys and villages of the Apennines.

Another possible stop is the “Elsa Silvestri” Civic Archaeological and Palaeoenvironmental Museum in Budrio, which tells the story of the Bologna plain from the Palaeolithic to the Middle Ages and is open on the third Sunday of the month or by appointment.
Check the official website for updates and opening times.