Name the 15 (16 with honorable mention) largest cities in the low countries of Belgium, The Netherlands, and Luxembourg. Population shows entire metro area.
Info for Belgium: http://www.worldatlas.com/articles/biggest-cities-in-belgium.html
Info for the Netherlands: http://www.worldatlas.com/articles/biggest-cities-in-the-netherlands.html
There were lots of conflicting sources but I chose this one to cite both countries