The village is of Roman origin, a place called Ad Padum (Al Po) in the imperial era, later known as Kalendasco in the Lombard era. The importance of Calendasco during the early Middle Ages is demonstrated in imperial papers. Calendasco was a fiefdom of the Bishop Count of Piacenza since 1000, a period to which the significant buildings of the village date back: the castle, the ancient church, and a hospital for pilgrims, also of the Franciscan penitents. In the village of Calendasco, there is an attested ancient Lombard xenodochio, whose vestiges remain under the current hospital, which belonged to the penitent Tertiaries of Saint Francis. The penitents who managed the resting place for pilgrims on the Rome or Francigena road always took great care of this place, and it is precisely thanks to the Via Francigena towards the Po that the “hospitio” takes on local value as a fundamental stop. It was also the site of Saint Conrad’s first retreat upon his conversion. In the town, the Parish Church, its Castle (private, visible only externally), which, together with the many other manors in the area, marks and distinguishes the landscape, the Hospital, and the Hermitage of S. Conrad are worth visiting. The castle, with a cylindrical tower, which can be seen next to the village church, preserves the architecture of the late 13th-early 14th century, with a drawbridge entrance on a moat. The oldest receptacle is located next to the building, with a drawbridge entrance. In the square in front of these imposing buildings stands the massive fortification, which served as stables for horses and stables for cattle. The first critical nucleus is the receptacle, built by the will of the Bishop of Piacenza, feudal lord of the place, in the early years of the 1000s; the castle was built a century later. The family that ruled this fiefdom in the manor was the Confalonieri, the last feudal lord of Calendasco, Fabio Perletti. The church of Santa Maria Assunta is the parish church of Calendasco in the province of Piacenza. It was already mentioned in Lombard documents, with the right to tithe. In ancient documents, it is remembered as the church of Santa Maria in Monticello, built on a mound of earth to protect it from the floods of the Po River, which flows a few hundred meters from the town. Even today, it maintains the original place: anyone approaching the city cannot fail to notice the imposing building of worship that stands on this promontory. Inside, the apse, frescoed in 1971 by the Piacenza painter Ricchetti, stands out. The parish church also houses nineteenth-century paintings by Faustino Perletti, count of Calendasco (b. Calendasco, 1815, d. Florence, 1878). As the first mayor of Piacenza and a lover of art and painting, Perletti obtained the famous “Botticelli tondo” as a gift to the city, a valuable work by the great Florentine artist. Calendasco is part of the route of the Via Francigena, or Romea, as the Archbishop of Canterbury Sigeric crossed the Po here in the year 990 AD during his trip to Rome to receive his investiture from the Pope. But even more remarkable is that on the territory of the Municipality, there was the ancient Roman port of Piacenza. At the port of Calendasco, the boats had to pay a tax for docking or just for transit in the direction of Venice or Pavia. The area is part of the routes of the Via Francigena: near Calendasco, there is the Sigeric ford, from which pilgrims can cross the Po via a small river boat to reach the Lombard bank. The Po River offers beautiful views of the surrounding area thanks to its characteristic landscapes.

Squeezed between the Luretta stream and the banks of the Trebbia, the town opens into a flat area a few kilometers southwest of the capital.
In the village, the Parish church the Parish Church dedicated to San Michele is worth a visit.  Already documented in 1132, it was rebuilt during the 18th century. On the main altar, a single nave church with side chapels stands an altarpiece by Robert De Longe.
The ancient castle remains are now part of a privately owned farmhouse in the countryside. In the municipality, there are some interesting private villas; Villa Marchesi by the architect Gazzola represents a twentieth-century example of the neo-Renaissance style.
Some summer events of the Valtidone Festival currently occur in the villa’s Italian garden.
The Municipality of Gragnano decided to protect two products, the burtléina and the “spisigona” cake.
Near the town center along the Trebbia River, an appointment with music for the traditional Orzorock festival.
In the surrounding area, Gragnanino Villa Douglas-Scotti (private home), the Sanctuary of the  Madonna del Pilastro.
The castles of Campremoldo di Sopra, Campremoldo di Sotto, and above all, Castelbosco – inside which the Shit Museum was inaugurated in 2015 – although visible only from the outside, it is nevertheless worth a visit as, together with the many other manors present on the territory, it distinguishes the Piacenza landscape.
The municipality of Gragnano includes an area belonging to the Trebbia River Park, characterized by the transit of migratory birds and the spontaneous flowering of various species of orchids.