Parrano owes its name to the Latin parra, an unknown and ominous bird often identified with the hoopoe or the owl. It first appears in this way in a document from the late 13th century, although numerous artifacts testify to human habitation in the area since the Upper Paleolithic.

The discovery of a green statuette carved from steatite—the so-called Green Venus—along with the remains of animals and burned grains suggests that the site was dedicated to religious practices. Tombs of Etruscan and Roman origin have also been discovered in the area, and the village plan, whose checkerboard layout recalls the layout of Roman camps, suggests that the area was also inhabited by these peoples.

Later, the bishops of Orvieto built a five-story castle there, overlooking the Chiani Valley. It was first remodeled in the 18th century by Marquis Francesco Ruspoli-Marescotti, who transformed it into a stately residence. Then, in the 1970s, Marquis Franco Fantauzzi had it cleared of the buildings that had been added to it over time.

The castle is first mentioned in a document from 1118 in which Bishop Guglielmo of Orvieto invested Bernardo di Bulgarello with the title of count, with feudal privileges over Parrano in exchange for an oath of fealty and a promise not to cede it to anyone. This was the first step for the Bulgarellis in controlling and administering a territory that also included Monteleone d’Orvieto, Civitella dei Conti, Montegiove, and even Castel della Pieve (now Città della Pieve). A vast and indivisible territory administered by various branches of the family, each taking the name of the specific fiefdom (counts of Parrano, counts of Marsciano, of Montegiove, and so on). Over time, the Counts of Parrano clashed several times with the bishops of Orvieto, but the fiefdom managed to maintain its autonomy until the abolition of feudalism in 1816.

At the foot of the hill where Parrano Castle stands is the thermal park, recommended for those suffering from digestive or liver problems. The area is also famous for a system of karst caves known as the Devil’s Dens, where thermal waters flow at a temperature of 28 degrees Celsius. Bronze Age artifacts, such as hut bottoms, ceramics, terracotta, necklaces, and animal bone fragments, have been found in the meanders of these ravines.