Italy's biggest retail bank has turned its historic headquarters in Milan's central La Scala square into a majestic modern art museum displaying Italian post-war works from the likes of Lucio Fontana and Renato Guttuso.

Palazzo Beltrami, a superb Milanese building which blends Neoclassical style with eclectic features, was built in 1911 as a prestigious new head office for Banca Commerciale Italiana, now part of domestic bank giant IntesaSanpaolo.

Nearly 200 works of art, all from IntesaSanpaolo's huge art collection, are on display as of this week in the same early 20th century halls where clerk desks and cash counters stood for 100 years.

Even the bank's restored vaults will be turned into exhibit halls, hosting a rotating selection of paintings and sculptures.

"The main bank hall is now the key museum hall," said architect Michele De Lucchi, who directed the project.

"We have left portions of the original cash counters, that are now an integral part of the exhibition space."

The newly inaugurated Cantiere del '900 exhibition is part of a broader museum complex called Gallerie d'Italia that belongs to IntesaSanpaolo and is set across from famed opera theatre La Scala and by the elegant shopping street Via Manzoni.

From Informalism to Pop Art, the collection aims to represent all the leading artistic movements from the 1950s to the 1990s. It is entirely made up of Italian works, many from the Lombardy region where Milan is based.

A whole section is dedicated to the emblematic Fontana, known for his Spatial Concept series, monochromatic paintings and other works with deliberate holes or slashes in them.

Other masterpieces include abstract paintings from Emilio Vedova, one of the most important Italian painters of the post-War era, collages from Alberto Burri or works by MAC (concrete art) movement founder Bruno Munari.

"For Italian banks, even the smaller ones, it has been a tradition to collect art and documents from their local area," said Giovanni Bazoli, Supervisory Board Chairman of IntesaSanpaolo.

"These masterpieces were however enjoyed by just a few people. I had two works of Umberto Boccioni in my office, that are now on public display."

The modern art collection complements a selection of works from the 19th century also from the bank that opened to the public last year and is hosted in the adjacent Palazzo Anguissola and Palazzo Brentani.

(Reporting By Lisa Jucca, editing by Paul Casciato)