In 1295, during the Sicilian Vespers, the Parliament which declared deposed James II of Aragon as King of Sicily, replacing him with Frederick III, was held here.

It also houses a medieval keystone, a 16th-century cannon, parts of an ancient Roman mosaic showing the months, a 16th-century inscription mentioning a castellan from Toledo and a statue of Ignazio Paternò Castello Principe di Biscari, by Antonio Calì, displayed with a copy of his book Viaggio per le Antichità della Sicilia.

This room and those following it display finds from the city's Roman theatre, including a huge headless statue, a torso of Hermes and a plinth found by Biscari in 1770 showing a trophy crowned by two Victories and two barbarian prisoners on its sides.

The main works exhibited here include: This houses displays of clay statues of subjects such as Aphrodite, a small dog fighting a cockerel, a nymph on a rock and a prehistoric head.

Particularly notable is a colossal ram, whilst the most important work in the room is a fragment of a cavalryman, probably from a historiated column, found near porta Carlo V. Named after its previous use as a storehouse for salt, it now houses a mosaic showing a head, thought to be an allegory for Africa, and a bust of an Egyptian woman.

It also houses a 420 BC marble relief of Demeter and Kore found on Montevergine hill in 1930 and several Greek vases such as the red-figure Crater with Perseus and Medusa from excavations in Camarina.

It also houses works by Natale Attanasio (Sunt Lacrima Rerum, best known as "Le Pazze"; Women in the Fields; Tasso and Cardinal d'Este) and Bernardo Celentano (Provenzan Salvani in the piazza del Campo).

This large room houses temporary exhibitions as well as sculptures, bas-reliefs, inscriptions from Certosa di Nuovaluce and an urn by the Gaginian school.