On the Hebrew calendar, the Jewish holiday Purim is celebrated on 14 Adar to commemorate the Jews defeat of the Persian army (see our Purim entry). Although that story is true for most of Israel, the battle continued for a second day in the walled city of Shushan.
So when the sages instituted the Jewish holiday of Purim to be celebrated 14 Adar, they made one stipulation: cities which were walled during the time of Joshua should celebrate a special Purim called “Shushan Purim” on the next day, the 15th of Adar. If Shushan Purim happens to fall on Shabbat, then the Jewish holiday’s festivities are be broken up into three different days, from the 14th through the 16th of Adar.
Where Is Shushan Purim Celebrated?
Jerusalem was definitely a walled city in the time of Joshua, so Jews living within the walls and in the suburbs and towns less than one kilometer form the city walls observe the Jewish holiday Shushan Purim. Obviously, the Jewish holiday is also celebrated in Shushan.