Girl Reading a Letter at an Open Window is currently undergoing a restoration at the museum location.  You can follow along with the fascinating details of this project on their website.

The Art of Painting was once stolen by Adolf Hitler during World War II.

Hitler illegally amassed a huge amount of artwork during WWII for a museum that he intended to build, which he called the Führermuseum. He hid most of the irreplaceable artwork in salt mines in and around Germany to protect the art pieces from Allied bombing. A group of Allied soldiers, called The Monuments Men, were charged with the task of finding all of the famous artwork that Hitler had stolen throughout Europe. American soldiers found Vermeer’s The Art of Painting and his painting The Astronomer in a salt mine at the end of the war, along with more than 6,500 other famous works of art. The mines were discovered by both American and Soviet troops after the war.

You can read more about this topic in an article called The True Story of the Monuments Men by Smithsonian Magazine, at the Monuments Men Foundation website or at Wikipedia.

The story of The Monuments Men was also made into a movie in 2014 starring George Clooney and Matt Damon.