Warning: This graphic requires JavaScript. Please enable JavaScript for the best experience. Of all the great masterpieces of early 20th-century art, Henri Matisse ...

'It’s like a reverse strip club where you’re the stripper,' says my friend in jaw-dropped disbelief. He, like me, is sitting naked and sweating in a mega-sized sauna alongside 300 other nude bathers.

Billed by organisers as a "swim demonstration", the gathering saw swimmers cool off from the summer heat with colourful bathing costumes and even the odd inflatable raft against the backdrop of Berlin ...