Nowadays, if you say a couple was ‘married in city hall of the 13th’ it just means they both said oui (yes) here in this building on the Place d’Italie.
Until 1860, however, Paris only had twelve arrondissements, so in those days if you said a couple had been ‘married in the city hall of the 13th’ it meant they weren’t married at all, but were living together out of wedlock — living in concubinage, as the French would say.
When the time came to enlarge the city and add eight more arrondissements, the folks over to the west in Auteuil and Passy were supposed to get the number 13, but they refused, not because they were superstitious but because they didn’t want people making jokes about their marital status.
Then as now, the people living over at that end of town were wealthy and powerful, so they succeeded in getting the number 16 for their elegant new arrondissement, and the number 13 went to the poor working-class folks on the banks of the Bièvre.
(I got this information from www.parisinsolite.net. But you can also find it in www.parislenezenlair.fr and probably dozens of other websites and books.)

City Hall of the 13th arrondissement
After the enlargement of Paris in 1860, new City Halls (Mairies) were built in all twenty arrondissements. The one in the 13th was built from 1866 to 1877 on the north side of the Place d’Italie by an architect named Paul-Émile Bonnet (1828-1881).

Stairwell in the City Hall of the 13th

Zadkine’s Return of the Prodigal Son at Place d’Italie
In front of the City Hall of the 13th there is a sculpture called ‘The Return of the Prodigal Son’ by Ossip Zadkine (1890-1967). Zadkine’s Paris atelier has been preserved and is now a museum, the Musée Zadkine, which just a short ride from the Place d’Italie by bicycle, only about 2 1/3 km. Just ride north on Avenue des Gobelins and turn left onto Boulevard de Port Royal, which has good bike and bus lanes. At Port Royal find your way across the square and ride a short ways up the Rue d’Assas to the museum.
My photos in this post are from 2013. I revised the text in 2018.
See more posts on the 13th arrondissement of Paris.
I think I remember this from VT – very interesting 🙂
Thanks, Sarah. Yes, I did use to have this on VT.