Although Amsterdam is the most famous city in the Netherlands, the city of Amersfoort is nice as well. Click on the blue circle to see a picture of the beautifull Koppelpoort.
library(leaflet)
url <- "https://upload.wikimedia.org/wikipedia/commons/3/39/Koppelpoort_Amersfoort_Cropped.jpg"
leaflet() %>% addTiles() %>% addCircleMarkers(lat = 52.1589771, lng = 5.3830483,
popup = paste0("<img width=\"200 px\" src = ", url, ">"))