I have quite a lot a fascinations in nonfiction (science and history), but to save some time, I'll mention them here only one at a time on days when I have the time to post here.
One of my many fascinations is the continent of Antarctica. I'm not exactly sure what it is about it that fascinates me so much, but I'm guessing it might be because, in terms of exploring new places, it's kind of like a bridge between the Americas and the Moon. Antarctica is like the Americas in that it was discovered by oceanic explorers and has been the site of many famous expeditions, and it is like the Moon in that it has no native people at all and the conditions there are so harsh that anybody going there will need to bring a lot of supplies for even basic necessities.
One way I can tell I have a mild fascination in something is that I've at least once spent an entire day on Wikipedia to learn more about it. I can definitely confirm I've been on Wikipedia more than once to read about everything related to Antarctica, particularly the explorations of the early 20th century.