>>532537484
Castles come in many shapes and sizes. Skyrim doesn't have much in the way of medieval castles other than maybe the city of Solitude and some of the forts on the map.
Something you may find interesting are things like Norman castles, mottes and baileys, and of course there's later styles of castle that you may be more familiar with. searching terms like "welsh castle" will also net you good results for ruins.

Ultimately the point of using these references is not to copy them 1 for 1, but to see what they did and apply it to your own builds.
Pic related is a historical Norman castle. It's very blocky. The stairways are all inside of the towers, and there's multiple floors.