This topic really deserves a steam or sauna in the US answer and a European answer. I have never encountered a co-ed naked steam or sauna facility in the US. There are a bunch of clothed ones. I had a good experience in Schveningen (sp) the Netherlands. That is a near in suburb of The Hague. It is called Vitalsee spa and is always nude. They have male hours and female hours and "mixed" hours.I was staying at an adjacent hotel and goe in about 1PM, had not slept on the plane and had a 6PM dinner appointment. Did not dare lay down, looked in the hotel attractions blurb and saw and ad for a spa. That was just what I needed. I put a bathing suit in a bag and went to the spa. The lady took my money. gave me a towel and a robe and directed me downstairs, where there was only one door. I went back upstairs and asked which was men' snd which women's? Lady said there is only one common dressing room as "bathing costumes are unsanitary and not permitted. I went back downstairs and got undressed, there were two women in the shower room, who did not bat an eye when I walked in. The facility was excellent, with steam rooms of different temps.jacuzzi tubs and a large pool. Clientelle was mostly older, a few kids and some stunning younger adults, male and female. It was matter fo fact, not cruisy and a lovely place to shake off trans Atlantic soreness.
We Americans have to shake off our prudishness and get real. I, of course, told my wife about it and a year or so later, we were touring Europe and she asked if I would take her to "my nudie" place. We went and she too enjoyed it.
Cincinnatus