This reminds me of the time I was traveling in Switzerland with my family. The hotel I was staying in had a sauna - two actually, one for men and one for women. In between the two there was a shared tanning "booth". The booth was actually just an alcove with a privacy curtain. One could easily tell when the tanner was occupied and there was no reason to linger in the hall if it was.
You never knew when someone might come by, to enter or leave one of the saunas. Nevertheless, once I noticed my aunt entering the tanning facility as I was passing. I waited a few minutes and then headed back. I couldn't linger, for fear of being caught snooping, but I did manage a quick peek behind the curtain. To my delight, I saw the my aunt was completely naked except for eye protectors and a pair of stereo headphones plugged into her walkman.
Immediately I saw the potential. I couldn't resist. I took a quick glance around and then slid the curtain completely open and quickly went on my way. As I said, I couldn't linger, as anyone could come by at anytime. Nevertheless, it tickled me no end, picturing the my aunt completely exposed, listening merrily to her music, oblivious to her surroundings. I waited in the bathroom as long as I could without raising suspicion and then headed back.
The curtain was still open and the my aunt was still clueless, so I quickly returned and went back to the sauna. To this day, I have no way of knowing if anyone else saw her during the long minutes she was exposed and how she found it out she was on displaying her assets to the world.