Party40Down is a swingers party organisation for couples and single ladies aged 40 and under — the name is a maximum age, not a minimum, and it is the single most misread thing about them. Their own description of the crowd is why the age cap exists: every kind of swinger has been finding their parties for years, which gives them a mix of experienced regulars, newcomers, and couples who are simply curious about erotic parties. If you are both over 40 they point you at their sister organisation instead.

They claim, plausibly, to be one of the most active parties in the Netherlands and Belgium, and they attribute that partly to a hard line the rest of the scene does not always take: a zero-tolerance policy on party drugs. Their reasoning is characteristically blunt — it means guests are interested in each other rather than in the ceiling or in stamping along to monotonous beats all night. Party sizes range from intimate evenings of twenty couples to nights of around a hundred and twenty.

The house rules are unusually explicit and worth reading before you book. No single men — including no unaccompanied men in the erotic areas. Everyone, men and women alike, changes into good lingerie immediately on arrival, and footwear is required downstairs for safety. Phones and any recording equipment are banned outright and must stay in a coat, bag or locker; they are not to be used in the changing room either. No party drugs, before or during, and no excessive drinking. Respect is the stated baseline, with no means no, and misconduct means removal without a refund.

Two practical quirks. There is no online ticketing at all: you sign up by email or through their SDC party profile, before the day itself, and the guest list lives on SDC. And they enforce attendance — two unexplained no-shows and you are no longer admitted. First-timers can ask to arrive half an hour early for a guided tour, which is a genuinely thoughtful touch for a first swingers party. Browse EroticAdvisor for the next Party40Down dates and house rules.