Some great stories in this topic! Thought I'd finally share my own as well (also my first post here). This happened a bit over a year ago, in Summer 2015. Feel free to ask and comment
Me and my fiancee (we're both 26 now) spent the 2015 Midsummer festivities at our friend's cabin. Both mine and her friends were gathered at the cabin to celebrate the nightless night. We arrived only on the second day of the party. It was still early in the day so most of the guests (the girls especially) were quite hungover from the night before. Among outdoor games and barbeque, sauna is an integral part of the Finnish Midsummer. Our custom is always, that the first turn is for the ladies and the second shift is of mixed gender. When we arrived to the cabin, one of our friend had already heated the "morning" sauna. When asked, none of the girls were keen to go to the sauna that early, so the guys occupied sauna. We walked to the sauna building on the shore, and my fiancee stayed at the cabin. Before I went, I asked her if she would like to come too, but she said she wanted to chat with the girls now.
In the sauna, five of my best mates (yes I remember clearly who they were
) told me about last night's action. About 20 minutes later, we had gone for a swim and come back to the sauna room, when there was a knock on the door. From behind the door, my fiancee was asking whether she could join us. This was allright to everyone in. That my fiancee eventually wanted to come was no surprise to me. She was in good terms with my buddies too, really talkative and loves the sauna. But what did surprise me when she entered the room was that she was all naked. Even though some of the girls had sometimes been naked in the mixed sauna, my fiancee had always kept a towel on. So none of these friends had ever seen her naked (or even topless) until now. Rarely even in the bikini.
She's fit 5'6, has amazing ass and thighs and perky B cup breasts with big pointy and pinkish nipples. At that time, she also had this cute, cleanly shaved dark landing strip. I could tell my friends were at least as much surprised as me from the sight. But certainly didn't complain. Of course, no one did comment anything and the situation felt quite natural, actually. My fiancee acted like it was nothing (we were in the hot sauna duh
) and perhaps it wasn't. She kissed me, sat next to me and the talking went on. She crossed her legs so that a hint of hair was visible on top of her pussy. Otherwise she didn't shy or cover her breasts. The sauna room was pretty compact so with seven people, my fiancee's thigh was stuck with my friend's. Now and then I could spot one of the guys glancing at her fine pair. All of this is still clear in my mind because the situation was so unique and unexpected. Hasn't happened later, even though we haven't visited the cabin either...
When we were finished with the sauna, fiancee and one mate had exited earlier for a wash. As the rest of us entered showers it felt so hot to see her without me and with my friend cleaning themselves up. Then or now, I didn't feel jealous. I felt quite turned on actually because she had independently decided that nude was the way to go today. Plus that she was the only woman in there to have all eyes on her. The rest of the day and night went business as usual. We got drunk and had a really good time. All that we talked about the mixed sauna was when fiancee mentioned to the girls that "I won't come again with you since I already went with the guys". That mention turned me on as well. Later when we got home and had sex it felt so much hotter to fuck when I thought about the episode.
Three years ago, while she was an exchange student in Austria, she had visited mixed sauna and spa world. But they were strangers in there and being completely naked in front of my male friends was something I never expected! And won't forget.