What alternatives to the internet are there?

The internet is nice, don't get me wrong, but suppose you couldn't use it for whatever reason, what remains? Of course any network could be bridged to the internet, but I'm talking about something that could function independently, for example; the telegraph network, sneakernet, siprnet (maybe?).

What I'm thinking of is something like a global mesh or LoRa devices with enough caching to ensure delivery or something crazier that communicates via power lines or visible light or something, but doesn't depend on Tier-1 ISPs and telecom fiber and BGP etc.