On August 27, 1783, in Paris, Benjamin Franklin witnessed the world's first hydrogen balloon flight. Le Globe, created by professor Jacques Charles and Les Frères Robert, was watched by a vast crowd as it rose from the Champ de Mars (now the site of the Eiffel Tower). Franklin became so enthusiastic that he subscribed financially to the next project to build a manned hydrogen balloon.
Source: Wikipedia
A nationwide "Festival of the Supreme Being" was held on 8 June 1794 (which was also the Christian holiday of Pentecost). The festivities in Paris were held in the Champ de Mars, which was renamed the Champ de la Réunion ("Field of Reunion") for that day. This was most likely in honour of the Champ de Mars Massacre, where the Republicans first rallied against the power of the Crown.[70] Robespierre, who happened to be president of the Convention that week, walked first in the festival procession and delivered a speech in which he emphasised his concept of a Supreme Being.
Source: Wikipedia