Amsterdam's sauna scene splits into three types: wellness bathhouses like Sauna Deco, gay cruising spots such as Thermos Day/Night, and erotic or swingers' clubs, which tend to sit toward the edges of the city. Shower first, look after your locker key and never take your phone out. A shut door or a hand pulled away is a definite no, every time. At the clubs the entry fee generally includes everything (roughly €60–120 for couples), while single visitors are often limited to specific nights. Arrive sober, keep an open mind, and show respect to the professionals and couples who keep this world running.
Sauna club etiquette in Amsterdam starts long before you undress. There's a door on Herengracht that looks like the entrance to a bank vault: brass, unmarked, dignified. Behind it are steam, marble and a hundred years of the city keeping its secrets warm. The culture is quiet and runs on a code nobody prints on a laminated card, so walking in blind marks you as new before you've found your locker.