On all four sides at the top of the citadel, there are these small crawlyholes. Spotting positions for officers? Those officers must have been short of stature, as an impressive amount of stooping and scuttling was required to get into this space, which is maybe large enough for two persons to stand side by side. They're open at the top and the front side of the bottom, with only a grate, seemingly of a more modern design than 1862, preventing one's shoe from dropping 36 feet to the ground.