I entered an office building downtown on a weekday, late afternoon, rode the elevator to the top floor, took the stairwell another floor up, and pulled open the locked door -- only a slight tug was necessary to pull the latch past the electric strike. An alarm sounded, not very loud, while I passed through the door and entered a big penthouse machine room.

I went out through another door onto an L-shaped rooftop at one corner, and took a couple of pictures of the view.

I went back inside in search of other rooftops or interesting sites, and just as I was approaching what appeared to be the service elevator, a guy came out of it.

Of course I assumed it was security come to get me, so I immediately started explaining, in my dumb innocent voice, how, looking for a rooftop patio I thought I'd heard about, I'd found this door open, and maybe they should look into it? The guy had no idea what I was talking about, and it soon became clear that he was actually a building engineer, who had naturally assumed I worked in the building, and would probably have walked by me with a nod. It took a while to get him to understand that I was trespassing, and that I was trying to help him and building management prevent people like me trespassing in future. Oy. I should have kept my smiling mouth shut.