Yeah some kind of fucky configuration.

The root is:

http://archive.ubuntu.com

Which, if the ubuntu link is clicked, then drops you into the the real archive root... but the link is "appended" to the new path, but the same link is reproduced in the "new" folder. Click it again, and another segment added to your current path even though you're in the same root archive, ad nauseam.

I couldn't find this misconfiguration on stackoverflow, which leads me to believe someone at ubuntu is doing something especially special here.