Relatively Major Cities of Countries on the World Map
For each country consider cities whose population is at least 20% of the country's largest city. Exclude those having a larger city within 50 km (even if this larger city is in a different country). Exclude cities with less than 100,000 inhabitants. Good luck finding them all!
Blue dots indicate world capitals (dark blue agglomerations containing them), red dots indicate urban agglomerations without a main city