East of the river on Groton Heights, a completed work, Fort Griswold, commanded the harbor and the surrounding countryside. It was somewhat square with projecting fortifications on two corners and a projection on the east side. A deep trench surrounded the fort on three sides. The lower walls were faced with stone and were topped with a barrier of cedar pickets projecting outward. Above this was an earthen wall with openings (embrasures) for cannon. A tunnel-like passageway (sally port) led to a covered ditch, which ended at a battery for cannon southwest of the fort. A V-shaped earthen mound protected the gate at the north end. Barracks for 300 men paralleled the innermost wall and the magazine was set into the southwest bastion near the flagpole. The fort was in good condition and the magazine was full in 1781.