During the medieval period the Bolognese gypsum area was characterized by small inhabited centers scattered over the hills, generally fortified and gathered around a castle or a parish church. S. Pietro di Ozzano, for example, one of the fortresses defending the Via Emilia, originated from the inhabitants of Claterna who, after the destruction of the city in the 5th century, took refuge on the nearby hill.
A little further on is the Pieve di Pastino, which already existed in the 11th century and on which the network of parishes in the area will subsequently depend; decayed in the fifteenth century and survived only as an oratory until the end of the nineteenth century, it was then transformed into a civil residence.
Not far from the parish church, and historically connected to it, stood the female monastery of S. Cristina, which had vast possessions in the area.
The monastery, demolished in 1769, was located near the long ridge between the badlands known as Passo della Badessa.
Memory of the monastery remains only in the figure of the Abbess Lucia, later Beata Lucia da Settefonti.
A romantic legend has it that Lucia, after her death, miraculously saved a young man of the Bolognese nobility from imprisonment in the Holy Land, who used to climb the steep ridge to the church to catch a glimpse of it during religious services.
The stocks that imprisoned the young man and Lucia's body are kept in the nearby church of S. Andrea, on the slopes of Monte Arligo. Also in the territory of Ozzano, near Mercatale, not far from the park, is the Abbey of Monte Armato; restored after the last war, its simple Romanesque architecture and suggestive somewhat secluded location make it certainly worth a visit.
On the right side of the Idice, formerly in the municipality of San Lazzaro, stands Castel de 'Britti, an ancient fortified village at the mouth of the stream on the plain, in a dominant position on an outcropping chalk spur. Among the localities of the park it is the one of the oldest memory, mentioned in an eighth century document as "Castro Gissaro, quod dicitur Britu".
Belonged to Matilde di Canossa and then passed to Bologna, it was destroyed and rebuilt several times, testifying to its strategic importance; traces of the walls remain, a ruined entrance arch and the 14th century church dedicated to S. Biagio.
Also in the chalky heights around the Croara there were fortified centers: a writing of 1084 speaks of a castle "quod vocatur Corvaria", probably in the current locality "il Castello"; a short distance away, the small community of Miserazzano, of which the memory remains in the name of the plateau, owned a church and perhaps a fortified building, where the reddish nineteenth-century villa of the Negri counts was later built.
Finally, along Via della Croara remains the church of the same name, which was once part of the Abbey of Santa Cecilia, founded prior to the year 1000.