Brigadoon -- oh what a rare place it is!

from http://www.wordsmith.org/

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 spell that makes it invisible to outsiders except on one day every 100 years.]

"There is a feel of Brigadoon to Cooperstown, the lush village of baseball and opera tucked into the middle of an idyllic nowhere in upstate New York."
--Elisabeth Bumiller, Cooperstown, The New York Times, Jul 1, 2001.