Let's review here:
1. At revolving bridge - Press that red button to get the flashing lights code at top of the arch. Do NOT touch that button anymore.
2. Now go to the gondola and travel to other side.
- Enter passage and see an intersection door (this is the door that you need to close later on).
- Go forward and open doors as stated on the walkthrough.
- One of those doors (accessed by an oval door) is closed and that is the one you need to open.
- Go back now to the gondola (or through one of the doors to go the long way around to the metal doors in the building you first arrived here on) after you have unlatched and opened all the other doors.
- Once you reach the gondola and the intersection door close it.
- Go back to the metal doors in the building you first arrived here on to go back to entrance hallway and through the metal door with highlighted 2nd square.
- Then go to the closed door you saw earlier. It should be open now.
- Go forward and use the code you saw earlier.