The K13 is a men's sauna on the Klävemannstraße in Oldenburg — the street and number its name is taken from. It describes itself as a place for relaxation, recovery, fun and wellness among like-minded men, and admits over-18s only.

Inside there is a steam room and a Finnish dry sauna, a video room, a solarium, a rest room, an atrium garden, a bar with snacks and free internet, alongside a darkroom, a sling, a St Andrew's cross, a glory hole, a gangbang area, and both double and private cabins. Massages are bookable in the early evening.

The sauna runs a Youngster day on Saturdays, with free entry for guests up to 24 on production of ID against a small minimum spend, and a naked night of its own. Its published times date from March 2022 and are worth confirming before travelling; its Instagram, Bluesky, Threads and Romeo accounts are the more current source.