First choose any Europe 10K+ pop city by entering it and choosing it in the drop-down box. Then, name any Europe 10K+ city in each 100 km circle/ring as the rings expand outward from your city of choice, trying to name SECOND LARGEST city in each circle. The first circle will include your city of choice as a possible answer.
PLEASE NOTE - You must type a '.' (period) after each city to submit it to prevent answering another city with a name you would be have to type to get your answer. If multiple cities have the name you submitted, only the largest one will be counted.
You accumulate points based on the population of the city you named in relation to the second largest city in the circle. A smaller city’s point total will be the ratio of its population to the largest, so if you name a city of 75K people and the largest city has 100K, you get 75 points. Naming the largest city will get you points based on the ratio of the 2nd largest city's population to the largest city's.
When you run out of time or end the quiz, you will see the current ring’s 2nd largest city at right (under ‘Answer Stats’ by your coordinates).
For example, if you choose ‘Paris’ – you will be shown a circle of radius 100 km centered at Paris. Naming any city in this circle (including Paris) will cause another ‘ring’ of radius 100 km to appear outside that circle, however - you will want to try naming the SECOND LARGEST city you can to get more points. After completing that circle, you now need to name any 10K+ Europe city in the new ring (but not within any previous circles/rings), again trying to name the 2nd largest city. If there are not two cities within the next ring of that distance, the ring will keep expanding by that distance until two cities fall within it.
Quiz Takers 
doesn’t make sense that some multi word cities are included if the first part is 5 letters and some aren’t
for example Torre del Greco included but Torre Annunziata isn’t
Gioia del Colle is included but Gioia Tauro isn’tRosny-sous-Bois included but Livry-Gargan isn’t etc.
I have adjusted these – they are based on the full name and I had some computing total letters off the partial shortened name. But for some cities very often referred to using a shortened name (like Frankfurt) I go with the shortened, common name.
these were just 3 examples there are dozens of others too (like in France every city that’s “sur” or “en” something)
it’s a good thing that we don’t have to type full names in general but they shouldn’t appear on quizzes like these which ask for an exact amount of letters
for some reason the markers for Halle, Essen, and Lille aren’t disappearing (even tho they’re counted into the stats)
fixing this now – thanks.