In summertime, the app about the US National Parks seems to be appropriate.
Concordia University Online Nebraska wrote a very positive review of this app: http://online.cune.edu/national-parks-app-review/ and I hope that you’ll enjoy it as well.
The English description of the game is the following:
Guess all 59 US National Parks either from its photo or from the map.
Yosemite, Grand Canyon, Yellowstone, and 56 more parks!
Demonstrate your knowledge of the American wilderness and prepare for the new adventures!
It is one of America-centered apps, but my experience with 50 US States and US Presidents was positive. Some of photos in the app are my own, others are taken from the nps.gov website. It’s handy that every picture done by the US government employee is in public domain. This app makes me want to visit all those parks I haven’t seen yet. My count is 22/59 so far.