The Monuments Men (2013)

The movie is based on a book that chronicled the work of real people who labored to salvage the thousands of works of art that were looted by the Nazis during WWII.  They were a band  of mostly middle-aged men and a few women who interrupted careers as historians, architects, museum curators and professors to mitigate combat damage. They were called  the Monuments, Fine Arts, and Archives section of the Allies, and they found and recovered countless artworks stolen by the Nazis.
The movie got mixed reviews but I very much enjoyed it--there is a balance between the horrors of what the Germans did during the war and the men who risked their lives to save Europe's art heritage for future generations to enjoy.

The Allies knew of the salt mine at Altaussee thanks to a toothache--this is portrayed in the movie and is based on a true event. Two months earlier, Posey (one of the monuments men, played by Bill Murray)  was in the ancient city of Trier in eastern Germany with Kirstein (another of the band) and needed treatment. The dentist he found introduced him to his son-in-law, who was hoping to earn safe passage for his family to Paris, even though he had helped Herman Goering, Hitler’s second-in-command, steal trainload after trainload of art. The son-in-in-law told them the location of Goering's collection as well as Hitler's stash at Altaussee.

Hitler claimed Altaussee as the perfect hideaway for loot intended for his Linz museum. The complex series of tunnels had been mined by the same families for 3,000 years, as Stout (George Clooney) noted in his journal.  When Stout arrived there on May 21, 1945, shortly after hostilities ended, he chronicled the contents based on Nazi records: 6,577 paintings, 2,300 drawings or watercolors, 954 prints, 137 pieces of sculpture, 129 pieces of arms and armor, 79 baskets of objects, 484 cases of objects thought to be archives, 78 pieces of furniture, 122 tapestries, 1,200-1,700 cases apparently books or similar, and 283 cases contents completely unknown. The Nazis had built elaborate storage shelving and a conservation workshop deep within the mine, where the main chambers were more than a mile inside the mountain.  The work of these brave souls was largely fogotten, and kudos to Clooney for telling their story.