I suppose I might have once read that GNU Emacs had a mark ring—that is, a capped collection of marked locations in the current buffer. But I've never really thought about it.
I can see a lot of possibilities in the idea, though—it's implicitly a list of nominally important spots in the buffer, so of course it has the possibility of being useful.
There are two commands that have a lot of potential. Both are variations
on C-SPC (set-mark-command).
The first is simply C-SPC C-SPC—that is, set-mark-command applied
twice. The first time sets mark and activates it, the second deactivates
it so any further motion won't start establishing a region.
Having set the mark, you can next use C-u C-SPC, which is simply
applying the universal argument to set-mark-command. This will start
cycling back through the mark ring, with each invocation moving further
back.
This may just be something I have to use repeatedly even when I don't need to, to start finding situations where it will truly be helpful.