With a territory of 186.74 square kilometres (72.10 sq mi) and a population of 22,535 (2017),[3] it is one of the largest settlements in the Irpinia historical district and the modern province.

Irpinia is the name given to the area of the Apennine Mountains between Campania and Apulia; the name stems from the Oscan word hirpus, meaning wolf.

As a result of this, the three hills started to be inhabited, a high and easily defendable place, and it is here that Ariano proper was born, a fortified city in a strategic position; however its ancient and formidable defensive walls are hardly recognizable today.

In 1255, Manfred, son of Frederick II, besieged the city, which resisted strongly thanks to its walls and the combative nature of its inhabitants.

More than ten years later, in 1266, Charles I of Anjou rebuilt the city and gave it two thorns of the crown of Christ, still conserved in a reliquary within the Museum of silverware [it], beside the town's Romanesque cathedral.

All these events are commemorated every year (in August) in the Rievocazione Storica del Dono delle Sante Spine (Historical Reinvocation of the Gift of the Sacred Thorns) and the reproduction of the Incendio del Campanile (Belltower Burning), a pyrotechnic event that lights the main square of the city and the side of the cathedral.

Many shops and restaurants offer produce as bread, pasta, pizza, meat, cherries, Irpinia olive oil [it] and Caciocchiato [it], a typical cheese.

[10] Actually an ancient Hospitalis pro Peregrinis et Infirmis, along with a pavilion for lepers, was founded thereabout in 1410, but it was relocated in 1731 in the neighboring St. Jacob Palace, where today is the Ceramics Museum's [it] scientific and educational center.

From Ariano Irpino railway station [it] (located 6 km away from the town centre), daily trains reach Rome in 3h30, and Bari in 2 hours.