Another fascinating place we visited on our trip to Croatia was this massive monument in a remote area between Zadar and Zagreb.

Here’s a little background information on it:

• A Yugoslav World War II memorial on Veliki Petrovac, a remote hill that is the highest summit in the Petrova Gora range.
• Officially called the “monument to the uprising of the people of Kordun and Banija”.
• Construction on the monument began in 1980; initially planned to be made of concrete, the structure was built using stainless steel metal sheets supported by a steel frame, to a height of 121 feet with an observation deck at the top.
• The interior included a reading room, library, administrative offices, and an underground section for film screening, conference and other events, reaching 30 feet below ground. 
• The names of 34,392 fallen fighters and civilian victims of the war were inscribed on the inner walls.
• During the Croatian War of Independence in the 1990s, the monument was repurposed by the Yugoslav army.
• The interior was converted into a base that housed a signal corps, a military police company and an air defense platoon; a training center; and a storage facility for ammunition, weapons, and explosives.
  
  https://en.wikipedia.org/wiki/Monument_to_the_uprising_of_the_people_of_Kordun_and_Banija