In the main hallway, just to the left of the Google both, there’s a vent, labeled “Google Ventilation”:
Clicking on it takes me into the vents, with an initial message:
After crawling around a bit, I found a way to climb up (left). At first I had hoped it would be the exit, but it just another level of maze (right):
After exploring the second level, I found an exit:
On exiting, I’m dropped into Santa’s secret room, bypassing the badge challenge, and with a new achievement:
Had I not already gone in via the badge reader, I could have also have unlocked the achievement for getting access to Santa’s secret room this way.
The dialog suggested a map would be helpful. I completely agreed. In crawling the vents to find the exit, I made a map of the full maze (using everyone’s favorite Infosec tool, Excel):