The Palazzo Castellani, site of the Istituto e Museo di Storia della Scienza since 1930, nowadays Museo Galileo, is a building of very ancient origin, dating from the late 11th century. Known at the time of Dante as Castello d'Altafronte, from the name of the family who owned it until 1180, when it became the property of the Uberti, the Castello was inserted in the city's very oldest ring of walls. After having passed from the Uberti to the Castellani family in the 14th century, it was the site, from 1574 to 1841, of the Giudici di Ruota (magistrates or judges of the high court of the Grand Duchy); even today the coats-of-arms of two of the magistrates remain on the walls of the entryway and remind us of this function. No documentation exists on the functions of the building in the 17th and 18th centuries. During the first half of the 19th century, the Palazzo underwent large-scale restoration. After the Unification of Italy, the collections of manuscripts owned by the Biblioteca Nazionale (National Library) were transferred to the Palazzo, where they remained until the 1920s. The Palazzo has also housed the Accademia della Crusca and the Deputazione di Storia Patria per la Toscana. Today, the Museo Galileo occupies the whole building. The spaces have been restored and adapted to the new uses. The work of restoring the basement level, carried out over the two-year period 2002-2003, has brought to light the four massive stone foundation arches of the ancient Castello d'Altafronte.
Situated in the heart of Florence, on the Arno, near the Galleria degli Uffizi, the Palazzo is a Medieval building with a facade of bare stone. It rises for six floors and is distinguished by rounded windows and rusticated stone arches.
The Palazzo Castellani is the property of the Italian State, which in turn leases it to the Museo Galileo at a token fee.

Spaces and Functions

Basement
The basement areas, recently renovated and enlarged, contain versatile spaces destined for both research and for public activities such as conferences, seminars, temporary exhibitions, cultural events, etc.

Ground Floor
In addition to the entrance hall, ticket office and bookshop, the ground floor houses the introduction hall to the museum's itinerary, the instrument restoration workshop and some offices.

First Floor
Located on the first floor is the permanent exhibition the Medici Collections of mathematical and astronomical instruments by great Italian and foreign instrument-makers.

Second Floor
The permanent museum exhibition continues on the second floor, presenting the Lorraine Collections, originally displayed, starting in 1775, in the Museo di Fisica e Storia Naturale, founded by Grand Duke Pietro Leopoldo di Lorena.

Third Floor
The third floor houses the Multimedia Library / Research Library and the offices of the IMSS.

Fourth Floor
The fourth floor contains the book stacks for the Library and has work stations for the Institute's collaborators.

External Spaces
In addition to its seat in the Palazzo Castellani, the Museo Galileo makes use of exterior spaces which house the Multimedia Laboratory, additional library collections, the museum's collections not on display, its publications, etc.