Be sure to see the category tree directly at the top of the Items category page. It will show all pages in a collapsible tree display.
A lesson about abstraction
Observe the two colladogram charts below. One contains more of a stressed importance on adding just one extra tier of ranking and grouping in order to acknowledge that the things in it are separate. While this helps in a scope of detailed understanding, it does not make understanding how the content fits together any easier.
Look to the chart below on the right, to create a point, imagine the grouping of items without the third group entirely, and the fourth group was in its place. This would seem incomprehensible, how long would I be looking to find bone helmet? (its picture is a mask, take a quick look)
The small and linked chart is up-to-date. The big chart is just-for-fun, and a free lesson about organization.