The first entry is always the pin's source. Overall confidence is a weighted average of how firmly each reference supports the start and end times used above; a reference counts half as much for every 180 days older than the newest.
The Paris[3] sewer museum's own history page states tours "began in 1867, during the World's Fair" without naming an exact day, so the pin uses the Fair's opening date.
States guided tours of the Paris[3] sewers began during the 1867 Exposition universelle.
The official Paris sewer museum history page states: "In 1867, during the World's Fair, the public was permitted to visit the sewers in galleries whose height had been increased."
Something missing or wrong? Say it in your own words: a link that backs this pin up, a different start or end date and why, or a fact it lacks or gets wrong. The AI checks it against this pin's sources, searches for better ones, and adds any page that backs you up. The pin's own sources still count most.
