With Paris preparing to host the summer Olympics this year, the Seine has found its way back into the spotlight, as city officials scramble to get it clean enough for swimming before the competition begins. But it’s not the first time the river has attracted this kind of attention. The major artery running through the City of Lights has forever been the star of the show, the very reason the city exists at all. A new exhibition at the archaeological crypt underneath Notre Dame Cathedral explores the importance of the Seine to the people living near it, through objects that were excavated from i…