The museum Alessi rises near the cathedral, and takes the name from the homonym priest of Enna, lived between 1774 and The canon had collected pieces of rare beauty - paintings, books, prints, engraved stones, vases, ambers, shells, idols in clay, bronze and granite, either Greek-siculi that Egyptians, and above all Greek, Sicilian and Romans coins, in gold, silver and copper and important archaeological finds - that constitute the principal nucleus of the museum. The magnificent collection was surrendered from the heirs of the canon to the Vestry of the Mother Church in 1860, and was progressively enriched by private donations, with work deriving from churches and monasteries and with the imposing treasure of the same church.

Among the work guarded in the museum we find the beautiful pictures of the XVI, XVII and XVIII centuries, the valuable paintings on copper, the tryptich of Cretan-Venetian school, artists' works from Enna of the last two centuries, among them sketches, portraits and prints of S. Marquis, P. Glasses, L. Hen. Of notable relief the crown of the ” Madonna of the Visitazione”, work of skilled goldsmiths, characterized by a refined chromatic variety, exalted by the shine of the precious stones, above all rubies and diamonds; the " Pelican ", a jewel constituted by an enormous topaz set in the gold and embraced by rubies and enamels, probably work of an artist from Palermo.

Among the sacred furnish valuable are the silver chandeliers, the wine glasses in hurled silver, the shrines, the hanging lamps in chiselled silver and the exhibitor, as that radiated in gold, silver, enamel and gems work of S., and G. Mercury. Finally of extraordinary interest is the collection of coins, that includes besides Greek-Romans coins, datable from the V to the I century B.C.., also Ptolemaic, Byzantine, Arabs and Norman coins and papal medals.