Jutting out of one of the dock’s cliff sides is a concrete tube, its mouth partially sealed by flood gates. The bulk of the pen is complete, although much of the support infrastructure for servicing submarines was obviously left unfinished. Dangerously shaky scaffolding sits next to abandoned machinery gutted for its wiring long ago. Much of this underground area is dark, and flooded by stagnant water, thinly iced over and deep enough to drown in should the ice crack underfoot.