Mainz מגנצא
The city of Rabbeinu Gershom, Light of the Exile, whose ordinances shaped Ashkenazi life.
Mainz was the largest of the ShUM cities and the chief centre of learning in the Ashkenazi world before the Crusades. In the later tenth century Rabbeinu Gershom ben Yehuda taught here — Meor haGolah, the Light of the Exile: he corrected and stabilised the text of the Talmud, founded the school from which Rashi's teachers came, and issued communal ordinances.
The best known are the ban on polygamy and the ban on divorcing a wife against her will, to which is usually added the prohibition on reading another's letters. Formally binding on Ashkenazi communities, they became in time the norm almost everywhere.
In 4856 the community was destroyed by crusaders — more than a thousand dead in a day, according to the Hebrew chronicles — and destroyed again during the Black Death in 5108. In the same city, three centuries later, Gutenberg printed his first book.