Moat
A moat was a defensive structure consisting of a trench filled with  water.

In 2375, Julian Bashir suggested putting a moat around the Alamo to Miles O'Brien, so they could win the Battle of The Alamo for once. Their seeming nonchalance about threats to Deep Space 9 prompted Quark to remark that they ought to build a moat around the station instead. ()

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Architecture
Security technology