Puits Artésien de la Butte aux Cailles

You'll often see locals filling containers with the natural 28°C spring water that has bubbled up here from 600m below ground since 1893. It's free, safe to drink, and is said to have health-giving properties thanks to its rich iron fluorine content and low calcium levels (BYO bottle). The four-tap stainless-steel fountain was inaugurated in the year 2000; striking opaque panels describe the history of the source (spring).