=== data ===
50 European countries; 209 populated places
    name  population  area_km2  density
  Monaco     38964.0      12.0   3133.0
   Malta    502653.0     274.0   1836.0
Guernsey     62792.0      48.0   1302.0
 Vatican       825.0       1.0   1166.0
  Jersey    107800.0     127.0    851.0

=== saved ===
europe_folium.html       737 KB
explore_density.html     431 KB