In the real-time strategy game Starcraft, Nydus Canals are Buildings grown by the Zerg. They are underground (allegedly intra-creep) tunnel networks hollowed by (and made of) Nydus worms. It essentially brings two points on the map together for purposes of navigation. I think (but am not certain) the original Nydus canals only came in sets of two, and sending a unit into one made them exit the other. Starcraft II has more Nydus buildings / units, I believe some that can just spit out a bunch of unites that are stashed elsewhere but haven’t seen Starcraft II games that have achieved Nydusness.
The same device was used in Generals which started with the Command & Conquer design for RTS and added newer elements, many borrowed from Starcraft. The GLA* can create tunnel-network entrances. Units that go in join a unit reservoir that can be recalled at any tunnel network entrance. In Lord of the Rings: Battle For Middle Earth II, Dwarves and Goblins have similar abilities with Mines who also feature the reservoir.
Unrelatedly (except that thinking about one pinged thoughts of the other) I found a device that allows me to tunnel my LAN through the house’s power system, thus getting me an ethernet internet connection without stapling a long unsightly cable from the living room to my computer station. Science! Technology!
* GLA stands for Global Liberation Army, essentially a SPECTRE-like amalgamation of terrorist and revolutionary groups, possibly just an aristocracy-financed nonprofit to assure that disenfranchised, oppressed peoples have a fighting chance against their overlords.