The flooded metro is located on the side of an old expressway which is littered with decrepit pre-War cars. The entrance to the old metro station is located in the middle of a square at the bottom of a set of nonfunctional escalators. On the other side of the expressway lies a large raider camp, whose occupants can easily overpower a lower leveled player.
The station appears to have meant to have been named "Flooded Sewer". The files for the flooded sewer location refer to this specific flooded metro, and even hold files for the Shocker glove and an unused Metro sign. Since there is another location on the game map of the same name, it would seem that either at one point in development there was a mix-up, and this Metro was meant to be named "flooded sewer" but an oversight meant it never got round to being done, or some other situation occurred.