Secret Underground is one of the most widely travelled party organisations in the Dutch and Belgian scene, and the range is the point: fetish nights, sensual all-in evenings, castle and hotel takeovers, pool festivals in France and an annual week on Ibiza. Rather than owning a room, it converts other people's — turning a swingers club into what it calls an underground playground for adults, then moving on.

Two concepts anchor the calendar. Fetish Amsterdam — the successor to the sold-out Dark Fetish editions in the Westerunie — runs twice a year at Club Paradise in Amsterdam, where the whole club is blacked out and rebuilt with extra slings, a genuine scaffold, dark rooms and a heavy dance area. The Sensual All-In evenings are the other half: softer in tone, all-inclusive in format, held at Club Paradise in Amsterdam and at the Buddha Club in Antwerp. Alongside those sit X-Treme Fetish, deliberately run without the restrictions the organisers say commercial fetish parties impose, and one-off spectacles such as the Dark Sins hotel takeover in North Brabant and a two-day presence at KamaSutrA in the Utrecht Jaarbeurs.

The house sound is driving techno mixed with what the organisation calls the SU Sound, and the crowd it describes for itself is broad: fetishists, sensualists, kinksters and erotic clubbers, with a stated preference for open-minded guests over a strict scene identity. Every edition is built around dance and play space in the same room — dance floor, play rooms, dark rooms, slings and chill areas, usually spread over two floors with a heated rooftop smoking area where the venue allows it.

Practical detail is a strong point of this organiser: it publishes hotel advice near its Amsterdam venue, notes parking, and runs its own dress-code page, which is enforced. Because the brand crosses borders, the sensible way to follow it is by edition rather than by venue. Browse EroticAdvisor for the next Secret Underground dates in the Netherlands and Belgium, and for the clubs it takes over.