Towers of Bologna

The Towers of Bologna are a group of medieval structures in Bologna, Italy. The two most prominent ones, known as the Two Towers, are the landmark of the city.

Between the 12th and the 13th century, the number of towers in the city was very high, possibly up to 180. The reasons for the construction of so many towers are not clear. One hypothesis is that the richest families used them for offensive/defensive purposes during the period of the Investiture Controversy.

Besides the towers, one can still see some fortified gateways (torresotti) that correspond to the gates of the 12th-century city wall (Mura dei torresotti or Cerchia dei Mille), which itself has been almost completely destroyed.

During the 13th century, many towers were taken down or demolished, and others simply collapsed. Many towers have subsequently been utilized in one way or the other: as prison, city tower, shop or residential building. The last demolitions took place during the 20th century, according to an ambitious, but retrospectively unfortunate, restructuring plan for the city. The Artenisi Tower and the Riccadonna Tower at the Mercato di mezzo were demolished in 1917.

Of the numerous towers originally present, fewer than twenty can still be seen today. Among the remaining ones are the Azzoguidi Tower, also called Altabella (with a height of 61 m), the Prendiparte Tower, called Coronata (60 m), the Scappi Tower (39 m), Uguzzoni Tower (32 m), Guidozagni Tower, Galluzzi Tower, and the famous Two Towers: the Asinelli Tower (97 m) and the Garisenda Tower (48 m).

The construction of the towers was quite onerous, the usage of serfs notwithstanding. To build a typical tower with a height of 60 m would have required between three and 10 years of work.

Each tower had a square cross-section with foundations between five and ten meters deep, reinforced by poles hammered into the ground and covered with pebble and lime. The tower's base was made of big blocks of selenite stone. The remaining walls became successively thinner and lighter the higher the structure was raised, and were realised in so-called "a sacco" masonry: with a thick inner wall and a thinner outer wall, with the gap being filled with stones and mortar.

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