Disappearing Gun

Fort Victoria, Devonport, North Island, New Zealand.
The threat of Russian expansion into the Pacific in the 1890s stimulated construction of Auckland's coastal defenses. Mount Victoria, being the highest of Devonport's volcanic cones at 87 metres was chosen for the observation and control post. The great disappearing gun was mounted here. It remained hidden in its pit for reloading between firings, it was then pumped upwards by compressed air and water to the firing position. After firing the recoil compressed the air and water in the cylinders again ready for lifting for the next shot.
It was fired only once - the vibration cracked the glass in many nearby windows and residents complained.

G for Gun in The Alphabet Site.