I would like to highlight the city limits (of Berlin, see example below), because you hardly recognise them. Do you have any ideas how to do this? Dashed, thicker lines in grey/black would be great.
library(ggplot2) library(ggmap) myLocation<-c(lon= 13.405057, lat = 52.528357) myMap<-get_map(location=myLocation, source="google", maptype= "roadmap", crop=FALSE, language = "German", color="bw") ggmap(myMap)
Thank you very very much in advance!!