The name comes from a leper hospital. In the Middle Ages, three miles outside Bologna, in a stretch of country called Ronco Maruni, a lazaretto was built — the via Emilia was a much-travelled road, and much-travelled roads carried epidemics — and a document shows it already working in 1214. Around that hospital the village was born, taking the name of its patron, Saint Lazarus the leprous beggar, and becoming first San Lazzaro di Roncomaruno and then simply San Lazzaro. There is one detail worth all the rest: the rector who administered the hospital was appointed by the sick themselves, who gave him the power to represent them and to manage their goods. The second part of the name is the river: Savena, from the Etruscan, means vein of water.
In the coat of arms is the bridge of the Sirens, which divided San Lazzaro from the papal territory next door, the countryside in green, and the motto Libertas — not a boast but a memory: the comune was born at the start of the nineteenth century, was promptly abolished and put back inside Bologna, and only won its autonomy again in 1827, by a motu proprio of the pope. Also in the nineteenth century count Gozzadini brought to light here a pre-Etruscan necropolis: together with nearby Villanova, San Lazzaro was one of the first witnesses of the Villanovan civilisation. Under the hills, meanwhile, lies a world: about two hundred caves cut into the gypsum, the Spipola cave with its doline, the Farneto and the Croara, and a karst complex running for over eleven kilometres — the largest in western Europe, today a world heritage site and protected by the Gessi park. At Farneto they still celebrate the Madonna della Cintura in thanksgiving: during the cholera of the eighteen hundreds, in that hamlet, nobody died.