I first heard about the actual Monuments Men when I watch The Rape of Europa on Netflix. It's a documentary based on the book by Lynn H. Nicholas about how the Hitler and the Nazis stole and looted art and treasures from private collectors and then the countries they conquered in WWII. In the last three or four years of the war, a small group of men with expertise in art and architecture was tasked by the U.S. to somehow protect and recover the art treasures and monuments.
I'm currently finishing up on Robert M Edsel's The Monuments Men: Allied Heroes, Nazi Thieves, and the Greatest Treasure Hunt in History, the book the movie is based on. I have plans to buy the follow-up by Edsel, Saving Italy,which covers the Monuments Men in Italy, practically an open treasure trove disguised as a country.
I suggest watching The Rape of Europa on Netflix. It's one of my favorite docs, and I can't tell you how many times I've watched it.