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.
I have also thought about Inca ruins because of its history. Thank you for this comment.
Wikipedia should have some of them covered, but I have to get it parsed differently than castles in UK for example. I will try to solve it later see if I can get some of them at least verified and include them on the map.
Yeah I think many of them are also listed as part of a larger archeological site and not individual buildings. The palace of the Inca at Machu Picchu doesn't have its own page on wikipedia.
For most ruins I fear they are not listed online anywhere at all
Edit: maybe turning it around and going with OSM data first and then linking the sites to wikipedia is more effective? OSM has pretty good searchable databases of archeological sites and individual buildings. The royal palace is listed as a "manor house" in close proximity to the "tourist attraction and archeological site" of Machu Picchu
Thanks! I managed to add something in Peru now https://thecastlemap.com/changelog/