At the beginning of the 20th century, electric-powered streetcars arrived and lighting was added. Progress also brought about a change in the appearance of the square and the evacuation of the market to another square. This was before World War II when the square became the center of Jewish life in the city. Here was the Jewish market, where the Jews of the city came to buy the things they needed before the holidays, like a chicken before Yom Kippur or the fruits for Sukkot.
When the Jewish Ghetto was created, during the Nazi occupation of Warsaw, the square was included within the boundaries of the small Ghetto. Here, too, stands the Church of the Assumption of Mary, which served the converts in the Ghetto, Jews who converted to Christianity in the past, but the Nazis saw them as Jews and put them in the Ghetto. Nazi racial theory, it should be noted, regarded Judaism as a race, that it was impossible to change, and not a religion, that it could be changed. Therefore, the change of religion did not change the fate of the converts.
Today, Grzybowski Square is still paved with stones and has not undergone significant changes since the war.
In 1941, when the Nazis liquidated the small Ghetto, the square remained closed to the citizens of Warsaw, and when the Polish underground uprising broke out in 1944, it became part of the area of battle. When the underground was defeated, the Germans destroyed and burned the western part of the square, the Arona Serdynera Jewish Synagogue and the church where the rebels had barricaded themselves.