I am not really into typical bar scene; I tend to throw parties at home where I invite people of various backgrounds/age and have evening of fun (having a music & photo/cinematography studio at home is handy). That is way simpler to do in those two cities I mentioned, where interesting people you know for a day or two want you even to attend their own social events; far more difficult when I tried to do it e.g. in Frankfurt. You get to know some very interesting people as locals tend to show off and bring you to some of their "local stars" and you get to soak culture directly (and on steroids). Still remember one guy bringing me to Bip Bip on Copacabana, introduced me to Alfredinho, and we spent evening discussing Brazilian life while having musicians performing various local songs, and you could soak the atmosphere, what makes Brazilians proud, the cracks and insurmountable issues they were facing daily, observe their blind spots my own culture handles better etc. You also get a crash course on what are advantages and disadvantages of their cultures if you are perceptive enough. With Germans, it's way more difficult and IMO not worth it for short-term stays (maybe Ossies are slightly different in this regard). Swiss & Austrians are even one level more opaque due to one more indirection layer.