ICI
JEAN SYLVAIN BAILLY,
PREMIER MAIRE DE PARIS
A ETE GUILLOTINE
LE 11 NOVEMBRE 1793

[Emblem of the city of Paris]

Jean Sylvain Bailly (1736-1793), was an astronomer and mathematician and one of the leaders of the French Revolution. He was the first president of the National Constituent Assembly and served as mayor of Paris from 1789 to 1791. After the Champ de Mars massacre in 1791, in which many of those demanding the overthrow of the king who was still reigning were killed, Bailly resigned and moved to Nantes.
In 1793, he was arrested and after refusing to testify against the king’s wife - Marie Antoinette, he was tried and executed in the Champ de Mars the place where the massacre took place and where the sign is located

The place where the sign is located was photographed on the same day Click for a larger image

Translation of the text on the sign:
HERE
JEAN SYLVAIN BAILLY,
FIRST MAYOR OF PARIS
WAS GUILLOTINED
ON NOVEMBER 11, 1793

[Emblem of the city of Paris]