>>27338155I personally like to chill underneath the Eifel Tower.
Champ de Mars, 5 Avenue Anatole France, 75007 Paris, France
Most of the Pokestops here have lures on them almost all the time, and there are a few that, with some good positioning, you can hit three at once.
Other than that, there's lists you can google up of ones that have high densities of Pokestops.