Battery DeRussy was once open to the public, which is proven by the sign that is now behind a barred iron door, which reads:

Battery DeRussy, completed in 1904 to mount three 12-inch disappearing rifles, is the largest of the Endicott batteries at Fort Monroe. This now extinct weapon was obsolete by World War II. The guns from this battery were dismantled in 1943.

HA 'extinct.' Like 12-inch disappearing guns all died off after some mysterious natural diaster, which I believe was known as "the invention of the guided missile."