The 3B is the bear bar of Cologne's Altstadt, in the room on Mühlenbach that ran for years as the Cox and made its name as a bear bar in the nineties. Part of the Roman city wall is built into the interior.
The bar is aimed at the bear community and says plainly on its own page that everyone else is welcome too, whatever they look like. Bear karaoke runs monthly.
It takes part in Cologne Pride and Bear Pride, which are the two weekends when the street outside is as busy as the room.