Fort Dorchester's mighty sally port! Unless it was the main gate. I'm thinking that the fort's main gate was the open bastion at its southeast corner, close to the Ashley River...which would make sense as the whole point of Fort Dorchester was to supply Charleston with powder, which would be delivered via the river...but there seem to be many question marks regarding this fort's layout. Perhaps you're wondering about the informational sign in the foreground: It is Designed for Defense.