Fortress Monroe, a fort built on Old Point Comfort, Virginia, to defend Hampton Roads and the approach to Norfolk. It has within it detached buildings for officers' quarters, barracks, storehouses, arsenal, workshops, the artillery school, etc. It can mount 187 guns. The fortress is six-sided, and is surrounded by a wet ditch, outside of which are batteries. It covers 80 acres, and cost $2,818,000. It is the largest fort in the United States.