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