I know Anne Frank's family lived in an attic, but how did people hide their Jewish friends from the Nazi authorities? Did people build secret bunkers or tunnels? Are there any particularly clever ways?
There are several known Polish medical doctors who alone saved thousands of Jews through their subversive practise. For example, Dr. Eugeniusz Łazowski, known as Polish 'Schindler', saved 8,000 Polish Jews from deportation to death camps, by faking an epidemic of typhus in the town of Rozwadów. Free medicine was given out in the Kraków Ghetto by Tadeusz Pankiewicz saving unspecified number of Jews. Rudolf Weigl employed and protected Jews in his Institute in Lwów. His vaccines were smuggled into the local ghetto as well as the ghetto in Warsaw saving countless lives.