World Tunnels

The World Tunnels are portals that connect two areas on earth and allow for very fast travel between them.

It is unknown whether or not these are/were used by the Elvish Government for fast travel, however, in the episode, Skyler says that he intends on using them to escape the Elvish Government. So the likely hood that they are still in use by the elves is unlikely.

In the episode "Your guide to living in a world with tunnels & trash bands", Skyler explains how when he was a "young child of seventy-two" he had a dream of a network of tunnels under the whole world.