Big Tank

Perhaps not as interesting as the Army Corps of Engineers model of San Francisco Bay,but the Navy's "Indoor Ocean" is certainly something. 

It's 240 feet wide, 360 feet long, and holds over twelve million gallon [sic] of water. This is the MASK, the maneuvering and seakeeping basin at the Naval Surface Warfare Center at Carderock.

The Dep't. of Defense, always at war w/ the English language.