Walther

A hushed hotel bar a few minutes into the Bahnhofsviertel, where the talking stays low.

The Bahnhofsviertel is loud until you find the doors that aren't. This is one: a small panelled bar off a side street, a proper Martini, and enough quiet to actually hear the person across the table. Walk in from the station side; you'll be there in five minutes and you won't want to leave in one.