Welcome is Bologna

The geology of Bologna

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“La creta, la selenite e l'arenaria / Di qui nasce il colore di Bologna / Nei tramonti brucia torri e aria […]”
“Clay, selenite and sandstone / The colour of Bologna comes from that / Towers and the air burn in the sunset […]”  Roberto Roversi


Texts: in collaboration with Geological, Seismic and Soil Survey of Emilia-Romagna

Salaborsa - Piazza Nettuno, 3

Salaborsa - Piazza Nettuno, 3

A crystal floor shows the archaeological excavations, which in 1989-90 revealed the existence of a building that was probably the seat of administrative offices of the Roman colony Bononia (II-I century B.C.). According to geological studies the subsoil of Bologna is characterized by the presence of gravel, sand, silt and clay that were deposited by the Apennine rivers. Clay and silt are in the old town centre, whereas gravel and sand are mainly to be found in the outskirts of the town, due to deposits from the Reno river and the Savena stream, which have often come close to the old town centre but have never gone through it. It was in this area, which was better protected from floods, that the Roman colony of Bononia was founded.

Around Piazza Maggiore

Around Piazza Maggiore

Bologna had very few stones, so terracotta has been widely employed since the Etruscan age, for this reason Bologna is called the red city.  In the façade of Palazzo Comunale sandstone is the protagonist of the portal and clay is the material shaped by Nicolò dall’Arca to form the beautiful Virgin with child that now decorates the façade. The façade of Palazzo del Podestà, with the bossage work consisting of three thousand floral tiles, by the famous architect Fioravante Fioravanti, called Aristotele, is completely made of sandstone. Palazzo Re Enzo instead is all made of bricks.

Palazzo D’Accursio – Piazza Maggiore, 6

Palazzo D’Accursio – Piazza Maggiore, 6

In the courtyard of the palace you will see the stone living room, donated to the city by the sculptor Pinuccio Sciola in 2006, an unusual resting place sculpted in trachyte, a volcanic rock that was widely used in Bologna during the Roman era to pave streets.  On the first floor of Palazzo d’Accursio, in Sala d’Ercole, you can see the fresco Madonna of the Earthquake, painted by Francesco Francia as an ex voto for the earthquake of 1505 which hit Bologna and its surrounding area. The seismicity of Emilia Romagna is linked to the evolution of the Apennines: a “young” mountain range that started to take shape about 55 – 60 million years ago and is still slowly but progressively rising.

Archaeological Civic Museum – Via dell’Archiginnasio, 2

Archaeological Civic Museum – Via dell’Archiginnasio, 2

The Museum documents the local history of Bologna, from prehistory to the Roman era, its main attractions are the collection of sandstone funerary steles in the section of the Etruscan Felsina and the Roman section, which mainly includes commonly used objects, symbols of the everyday life in Bononia.

Two Towers - Piazza di Porta Ravegnana

Two Towers - Piazza di Porta Ravegnana

Here we are, at the feet of the monument that is the symbol of Bologna: the two towers. The Asinelli Tower, the taller one (97.20 m) and the Garisenda Tower, the smaller one (47 m) that is clearly leaning. The basis of the Garisenda Tower is covered with selenite, with the characteristic dovetailed twinned crystals with a milky shine that resembles the reflection of the moon (selene in Greek). Selenite is a rock consisting of gypsum, originating from evaporated sea water.

Piazza Santo Stefano

Piazza Santo Stefano

The Santo Stefano abbey is an old complex of buildings from different periods, that were restored many times. Here local stone materials (sandstone, terracotta and selenite) were used together with scrap materials coming from the demolition of old monuments. The façade of the church of the Saints Vitale and Agricola (rebuilt at the end of the 19th century) has many fragments of green porphyry and Egyptian red porphyry, inserted in terracotta. Inside the church, among other attractions, there are two marble sarcophagi that support a Greek marble slab, coming from a Roman monument. In the Basilica of the Holy Sepulchre, seven African marble columns surround the sepulchre of Saint Petronius.

Strada Maggiore

Strada Maggiore

The portico of Casa Isolani, after the high wooden structures that are placed on selenite blocks, leads to Strada Maggiore. At the crossroads with Via Guerrazzi you can see on one side the famous sandstone Atlas figures of the façade of Palazzo dei Bargellini (1658) and on the other side the Renaissance portico of the Church of Santa Maria dei Servi, made of Istrian limestone and nodular limestone from Verona. Istrian limestone, extracted since the Roman period, is widespread throughout the city, where it arrived from the quarries of Croatia, going through Trieste, Venice, Ravenna and reaching Bologna by river.

Piazza Aldrovandi

Piazza Aldrovandi

We enter the square named after Ulisse Aldrovandi (1522- 1605), the father of modern geology. The word geology in Bologna originated from him. On the 10th of November 1603 Aldrovandi decides in his will that the discipline whose modernization he and Leonardo Da Vinci had contributed to will be called Geology or de fossilibus.

Via San Vitale

Via San Vitale

Here visitors can catch a glimpse of the second circle of the walls of Bologna: the gate Serraglio di San Vitale of the circle called Cerchia dei Torresotti, dating back to the last thirty years of the XII century. This part of the wall is made of terracotta and the arch is made of selenite blocks.

Via Zamboni

Via Zamboni

Here are two important museums of the nineteenth century, inaugurated in the golden period of geology in Bologna. The Geological Museum G. Capellini set up in 1860,  shows finds from the regional and national territory and rich collections of rocks, plants, invertebrates and fossil vertebrates, among which the skeleton of a diplodocus, 26 metres in length and 4 metres in height, found in 1899 in Wyoming. In the Museum of Mineralogy and Petrography Luigi Bombicci, founded in 1861, a very interesting section is the section on the Bologna phosphorus stone, a worldwide known variety of barite that is found in the badlands of Paderno.

Geological Garden Museum Sandra Forni - Viale della Fiera, 8

Geological Garden Museum Sandra Forni - Viale della Fiera, 8

A few steps from the centre you can take a walk through geology thanks to the route of the Geological Garden Museum Sandra Forni: 14 rocks tell the geological history of the Emilia Romagna region, a history that is revealed in the landscape of the hills of Bologna. The wild landscape of the badlands characterizes the upwelling areas of clay, shaped by the surface run-off. The majesty of the cliffs of Contrafforte Pliocenico (Pliocene Spur) expresses the resistance to erosion of the sandstones of the ancient shores of the Padan Sea; the karstic shapes (sinkholes, ponors and caves) show the presence of soluble rocks, such as gypsum.