Doom2 Level 5

OK. I seem to have level 5 "the waste tunnels" under control. My problem is
I cannot find any secrets and there is this one spot behind a jail that I
cannot get to, it has a couple of weapons behind there.
I am unsure how else to describe the area....it is blocked by a brick wall
on one side and I can see at a certain angle near the jail that the other
side is blue...might also have a logo.

So! Gimme a hint on how to acquire the weapons and tell me what other
secrets lurk around.

$$MF