Every now and then at work everyone has to work a Saturday, and on my weekend I had plans right afterwards. I took a change of clothes with me so I wouldn't have to run home, and after I clocked out I went to a bathroom in an area that is basically deserted on the weekends.
I went into the stall and started stripping down, leaving me only in my underwear. I started swapping clothes in and out of my bag when I realized, obviously, that I was only wearing my underwear. That thought started getting me a little horny, and since I knew I was alone, I took my underwear off too. I stood there for a few seconds not wearing a stitch with my penis getting harder and harder, then grabbed it and started stroking slowly. It felt really nice being naked in a place like that, so my mind got a little more risky and I opened the door and walked over to the sink. If anyone would have walked in I would have been busted, but that made it so much better. I could feel my orgasm coming fast, so I got on my toes for a little more height and started shooting all over the sink with a loud grunt. I don't know how much I shot, but there was a huge mess that even made it to the mirror. I admired it for a few seconds then wiped it all up, flushing the paper towel and getting dressed.
I don't know if anyone else has ever used that bathroom as a masturbation room or not, but I have done it a few more times since.