You can see three rivers. You'll have to answer correct on the river for the first city to appear. When you've answered correct, a new city will appear. When you've answered correct on all the cities by that one river, you'll move on to the next river. There's a total of five cities by each river. You can always switch river by clicking on the second row of another block.
Too hard. The ones on the Danube are all reasonable (except for Linz, which I've never heard of) because they're capital cities. I was able to get all of the ones on the Rhine because they're, at least, major cities. I guess I knew, in theory, that there must be an Orleans because there's a New Orleans, but I would never have guessed it. I'm aware of Tours, but it's so far down the list of French cities, I never got to it. There's a city called Angers? Four of the cities on the Loire are the four least guessed cities, with a drop-off of nearly 20%.
The placements are correct during the play, but you just reverse some cities in the correction (when we look at the cities on the map afterward)
So I've just entirely removed it