The Museum of Archeology was founded by Stefano Galli from Modigliana in 1867. Since 1980 it has been located in the Palazzo del Podestà, wich was built in 1225, the year Massa Marittima became a Free City.

The Palazzo del Podestà is a two-story travertine building. Its façade features several coat-of arms of the Podestas. Near the entrance there is a big iron bell, where people who were exposed at the pillory were tied. In a small hollow of the same wall there used to be a metal yardstick: the so-called "passo" (step) of Massa.

In past times the Palazzo was also used as magistrate's court and prison, as shown by some cells still extant on the last floor.

Ground floor
To the left of the ticket booth, a small hall hosts the Galli Collection.
In the wall of the staircase, two small glass case contain an impression of the Oreopithecus, a fossil monkey from the Miocene, and the valuable stele of Vado all'Arancio, dating from the 3rd millennium B.C.
The other two halls host finds from excavations in the area around Massa Marittima: prehistoric items from the numerous caves of the area, Etruscan and Roman findings, mostly from tombs.

First and second floors
The upper floors host finds from area A and area B of the Etruscan site near Lake Accesa. These finds, dating from the late seventh and all the sixth century B.C., can be traced to a mining settlement, as pieces of minerals were found between the short foundation walls of the dwellings, and this area is very close to the mineral-rich areas of Fenice, Capanne and Serrabottini.