1. Grande Synagogue de la Victoire — Opéra / Grands Boulevards (9th)
The Consistoire's grand synagogue, inaugurated in 1874 and still Paris's largest.
The Grande Synagogue de la Victoire is the principal synagogue of the Consistoire de Paris. Wikipedia credits architect Alfred-Philibert Aldrophe, with building begun in 1867, an inauguration in 1874 and public opening in 1875, in a Romanesque Revival style with Byzantine details. It was designated a monument historique in 1993.
Its site describes a modern Orthodox community of more than 2,000 families following the Alsatian Ashkenazi rite. The site lists weekday morning and evening services, Friday evening at 18:30 and Shabbat morning at 9:30; it gives no visitor or security information, so contact the synagogue (+33 1 40 82 26 73) before you come.
Good to know: Write or call ahead to ask about visits; services run daily and the site posts the times.
44 Rue de la Victoire, 75009 Paris