Arachnia was a fictional location.
While participating in Tom Paris' holodeck program The Adventures of Captain Proton, Captain Kathryn Janeway (in her role as Queen Arachnia) claimed that "It's lonely at the top" was a saying originating from Arachnia. (VOY: "Bride of Chaotica!")
It is unknown if this location already existed within the Captain Proton universe or if Janeway simply made it up.