The Pit: Navigating to 1st Furnace

The next destination after the Backup Generator is the first Furnace Room, which is reached via the Furnace Intersection. That is on a lower level off the east side of the SE Gallery. Walking: Turn right upon exiting the Backup Generator room, and take the ramp down to the acid trap. Turn left there, and follow that catwalk downward and around until it reaches an entrance marked with one yellow and two red signal crystals.

Jumping: From the entrance to the Backup Generator Room, jump across the NW gallery, aiming for the entrance to the Main Intersection below and a little left across the gallery (steer to avoid the catwalk and pipes spanning the gallery here). Cross through to the other gallery at the main intersection, and jump directly across the SE gallery the same way, aiming for the entrance you can see below with one yellow and two red signal crystals.

Whichever method you use to get there, just inside the entrance is the junction itself, where there are 3 drawbridges. The left drawbridge will be down at this point. Take it down a long corridor which turns & opens into the First Furnace Room.