CIA Museum

It's not open to the public (and you definitely shouldn't try to visit), but inside the Central Intelligence Agency headquarters in Langley, Virginia, there is a collection of declassified artifacts, weapons, documents, and other fascinating items collectively known as the CIA Museum.

Then-CIA Executive Director William Colby established the museum in 1972. The collection is said to include more than 3,500 objects of historical significance, including previously classified documents, specialized weaponry, unique uniforms, and even a purpose-built semi-submersible. Much of the collection was donated by current and former members of the CIA, as well as its previous incarnation as the Office of Special Services. According to the CIA, many of the objects the museum holds were designed, manufactured, and used specifically for intelligence operations.

Since the museum is located inside the CIA's heavily guarded compound, it's not possible to visit, but they often work with presidential libraries and other major museums to arrange public exhibitions elsewhere.