Vetus Auximum was founded by the same Greek colonists of Ancona; later it was contested by the Gauls and the Picentes until conquered by the Romans, who used it as a fortress for their northern Picenum settlement starting from 174 BCE. The walls were made of large rectangular stones which are still visible in some locations. It was a colony until 157 BCE. The family of Pompey were its protectors and resisted Julius Caesar in 49 BCE. Inscriptions and monuments in its town square attest to the importance of Osimo during imperial times.[3]
Osimo was a free commune by 1100 A.D. It was later returned to the Pope by Cardinal Gil de Albornoz. In 1399–1430, it was a fief of the Malatesta family, who built a rocca, or "castle", which is no longer intact. Osimo was again made a part of the Papal States, and remained so until Italian unification in 1861.
Osimo retains a portion of its ancient town wall (2nd century BCE). Under the town is a large series of tunnels with esoteric bas-reliefs. The town hall contains a number of statues found on the site of the ancient forum. The new castle (1489), of which parts remain today, was built by Baccio Pontelli.
Among the churches in the town are the following:[5]
Osimo Cathedral: (8th–12th centuries) The restored Romanesque-Gothic church has a portal with sculptures of the 13th century, an old crypt, a fine bronze font of the 16th century and a series of portraits of all the bishops of the old diocese of Osimo. The baptistery is from the early 17th century and also has a notable baptismal font.
