So I'm wrapping up the last of the Riddler challenges, and I only have one left. It's the one in the Pump Room in the Caves section of the map.
Trying to get there from the BatCave/Sewers, its blocked off by one of those electric fences. On the map, it looks like there's an entrance from Arkham West, but I don't see a corresponding entrance when I'm in that area of the map.
How can I get back into that area? Did I miss one of the control boxes somewhere? Is there really an entrance from Arkham West?
As to where I'm at in the progress of the game, my current objective is to go to the party.