Stroll through 480m of pungent tunnels in the sewer museum, which was recently renovated from 2018 to 2020. Here, you can learn about the development of Paris' waste water removal system, and discover the truth behind the city's one rat per person ratio. To enter this underground world, simply locate the kiosk by 93 quai d'Orsay in the 7th arrondissement and descend down the maintenance hole.