Berlin, Germany at the Artemis FKK club.

Took place 13 April 2016 in the evening, and a combined 212 escorts and clients were found.  After months of investigation culminating in a raid with 680 police officers, and nearly 120 customs officials, tax inspectors, and prosecutors, they made a whopping 6 arrests.

While the obligatory "trafficking" makes headlines in US and UK papers, the German news is clear: the raid was focused on finances to the tune of 17.5 million euro in social taxes, and evasion of 6 million euros in income taxes.  Moral of the story: pay the tax man his due!

The six arrest warrants were:
  2 against the operator of the brothel
  4 against women working there as housekeeping

Link below is to a German news agency in case someone else's translation skills are better than mine.  Damned if I can find the same article on the English site