I built this map from open data. Every point is one of 5,793 castles, fortresses, palaces and ruins across 138 countries: 2,591 castles, 1,180 fortresses, 934 palaces and 1,088 ruins. The density is the story. Europe blazes while most of the planet stays dark.
It is a curated atlas, not a complete inventory. Germany alone has an estimated 25,000 castle sites (According to some sources). A landmark makes the map when it has a real photo on Wikimedia Commons, a Wikipedia article and exact coordinates in Wikidata, balanced across countries so the map stays explorable. France leads with 351.
You can explore every one interactively at https://thecastlemap.com/ with photos, founding centuries and short stories, plus a daily Guess the Castle game. There are no ads or sign up, everything CC0 and free to download.
Cool map! I think more could be added to the US map if you include historic armories. A lot of those buildings are more castle-like than the fortresses listed. https://en.wikipedia.org/wiki/Category:Armories_on_the_National_Register_of_Historic_Places_by_state
A few specific very castley examples in new england: https://en.wikipedia.org/wiki/State_Armory_(Springfield,_Massachusetts)
https://en.wikipedia.org/wiki/Cranston_Street_Armory
https://en.wikipedia.org/wiki/Lynn_Armory
Thanks for the suggestion! I will verify them first and then add it to the map:)