I have tried to experiment with just doing it in Plots (which I often find easier as it acts as a general interface to many plotting packages), but I’m having some trouble, so it appears my response was too glib. This is probably a case where you need to use a specific package, like PlotlyJS or PyPlot, as suggested by others. Note that if are happy with using PyCall to call Python libraries you might instead consider using RCall and just do the visualisation with ggmap, if you are used to that. Otherwise, it’d be very cool to see what julia-native solution you could find with PlotlyJS.
To my mind map visualisations are many things - it could include everything from building maps from the bottom up with rasters and shapefiles (that’s what I usually do - see this question Overview of Geo tools for the current progress of this kind of functionality in julia), to an interface to google map’s API (which I don’t think exists right now), to simply plotting a heatmap and points on top of an image taken from the interwebs (that was what I tried). All of these approaches could lead to the nice map you posted.