coterminous koh-TUR-muh-nuhs, adjective:
1. Having the same or coincident boundaries.
2. Having the same scope, range of meaning, duration.

Coterminous is from Latin conterminus, from com-, “together; with” + terminus, “boundary.”

brigadoon BRIG-uh-doon noun:

An idyllic place that is out of touch with reality or one that makes its appearance for a brief period in a long time.

[From Brigadoon, a village in the musical of the same name, by Alan Jay Lerner and Frederick Loewe, based on the story Germelshausen by Friedrich Gerstacker. Brigadoon is under a curse that makes it invisible to outsiders except on one day every 100 years.]