Open the door in front of you. Go through the northern passage, and under the northeast doorway. Enter the southeast passage, go upstairs, run south, and head through the hallway until you find a switch. Press it, and jump down to the east. Go through the northern doorway, take the lift, and run along the walkway to the switch. Flip it, and go up the staircase to the east. Head out through the southwest to find the blue key. Take it, and jump back down to the platform. Backtrack to the first room, and enter the northwest path. Open the blue door at the end, and take the southern stairway. Open the next door, and flip the switch. Head back across the staircase and through the northern opening. You will come across a winding path above a lava pit. Navigate this path, and enter the alcove. Flip the switch to lower the red key, head back across the path, and grab it. Return to the first room, and open the red door to the east. Go downstairs, open the next door, and flip the switch.
Other points of interest
In the hallway leading to the switch that opens the path to the blue key, there is a section of the southern wall with a lightning bolt on it. Press on this to lower a secret door (sector 150), behind of which is a teleporter leading to a soul sphere on a post in the center of the map.