The Wikipedia List of Lists of Lists

For the more mathematically minded, this actually makes sense. You have a few things, you put them in a list. Then you have a bunch of lists like "People who died in 1954, People who died in 1955, ...", so you put that in a list: "1950 deaths". Then you realize, you have many of these things, lists that contain lists, so you creat the List of Lists of Lists. That's how we got here, I don't make up the rules.

But besides the mind-bending part of it, it actually is a good way to explore the encylopedia. Many have argued that it's just as good as any index by "branch" or "topic" of knowledge.