Austro-Hungarian fortifications on the Italian border
The Austro-Hungarian fortifications on the Italian border were constructed in the 19th and early 20th centuries to protect against invasion from Italy. Most were built in what is today the Trentino-Alto Adige region; some built outside this territory were ceded to Italy after 1866.
Source: Wikipedia — Austro-Hungarian fortifications on the Italian border (CC BY-SA 4.0)