The 39 Clues Wiki
The 39 Clues Wiki

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The Smithsonian Institution Building (aka The Castle), the Smithsonian's main administrative building

The Smithsonian Institution is a system of museums located in Washington, D.C. in the United States. The museums are funded by the United States government, and are thus open to the public for free. Some of the more notable Smithsonian museums include the National Museum for Natural History, where the Hope Diamond is stored, and the National Air and Space Museum, which contains Orville and Wilbur Wright's first airplane, the Wright Flyer I.

Isabel Kabra visited another Smithsonian museum, the National Museum of American History, searching for the location of the Machina Fini Mundi, and a group of agents affiliated with the Cahill family (Amy and Dan Cahill, and Atticus and Jake Rosenbloom) later visited the same museum while following Isabel. With the help of Dr. Nancy Gwinn, a museum curator, both parties were able to find a hint in the form of coordinates etched on the back of a compass owned by Meriwether Lewis and William Clark.