Traditionally, many Italian libraries did not allow patrons to retrieve their own materials, and even today, closed stacks are more common in Italy than they are in the United States.
If you visit an Italian library with open stacks, you won't see the Library of Congress (LC) call numbers that are typically found in American university libraries. Instead, many Italian libraries use Dewey Decimal Classification (DDC) call numbers to organize their books.
For example, the DDC call number for John Clarke's The Houses of Roman Italy is 728.0937.
Another wide-spread system of call numbers in Italy is the Universal Decimal Classification (UDC) System, which is derivative of DDC. Depending on the scope of your research, you may also come across unique classification systems in archives and special collections.