I had an interview in one of those fancy serviced offices. I got through security & took the lift where I was directed. Did the interview, and took the lift back down to the ground floor. But I didn't recognize where I was, and was wandering around trying to look like I knew where I was going whilst desperately trying to find the exit. Got increasingly panicky, kept retracing my footsteps, then I nearly got trapped in a deserted room. I eventually twigged I must have entered on the Lower ground floor.