The object of this quiz is to adjust each circle's radius so it contains the target population shown at the right but ONLY within Europe. When you click Start you will be shown a marker on a random populated Europe grid square (there are over 90K 10x10 km grid squares used for the data, courtesy of https://human-settlement.emergency.copernicus.eu/index.php). Also you will see an adjustable circle of radius 100 km to start. Adjust the circle's radius by dragging it until it contains the target number of people shown - this target will be between 5 and 100 million people. Then click submit. You are scored on how close your circle's population is to the target.
PLEASE NOTE: ALL of Turkey is included in counting population (not just European portion), and the portion of Russia west of 61.5 degrees E (just east of Chelyabinsk). Nothing outside Europe (such as Africa or middle east other than Turkey) is included toward the population count within a circle.
Quiz Takers 
Perhaps a list of the stations you’ve guessed somewhat like with the periodic table.
Possibly with a per letter scorecard
1st try 77 done
A National Rail stations quiz for all train stations in the UK would be neat.
More time. There’s no way you can get it all done in that time (yes, I see two people have done so, but I am very dubious). Also, it didn’t pop up afterwards with the top 50 most difficult ones. Was this intentional?
there’s 30 minutes now and there are bonuses along the way…so I bumped it up a bit.
Should have more time, I could have done way more with more time. Otherwise good 🙂
a ton of UK (especially London) new users here – so this is for you! let me know if i need to accept any alternates.
Mr. Holmes, first name Sherlock, would like you to know the street he lives on is the name of a Tubeway Station.
Very good quiz, thank you. Echoing gmaric.22, could have done with some more time. You’re asking for two seconds per guess which isn’t possible for us mere mortals.
ill bump it up a little soon