90 secs Countries of the World: by 1M City in Bordering Country, with a Map
When you type the name of a city having at least 1 million inhabitants, its country and the bordering ones will appear.
When you start, type any number to make countries with neither land border nor 1M cities appear.
Data from citypopulation.de
Thick borders indicate only one city will make that country appear: if the border is violet, that city is in that country, if the border is blue, it is in a neighbouring country