While Germany may have a reputation for being more tight-laced than neighbors like France or Italy, it's also famous for making clothing optional - oddly enough, given average annual temperatures hovering at around 13 degrees Celcius (in the mid-50s Fahrenheit). Here are a few places you can get naked or see other people getting naked in Germany without being ashamed - and without getting arrested.
Germany
has long been famous for its so-called "Freikörperkultur" (FKK), or
Free Body Culture. Despite the obvious advantages of clothes - in
particular, warmth and protection from rain and sleet - the tradition
has persisted over the decades. Though sports have been associated with
nakedness for millennia (think Ancient Greece), communal public
stripping came into practice in Germany in the late 19th century.
Clothing styles were becoming less restrictive as women undid their
corsets and men tossed aside their multi-piece suits.
https://www.dw.com/en/where-to-get-naked-in-germany/a-19153265