The Aarnivalkea, in Finnish mythology

Finnish mythology

Finnish mythology is the mythology that went with Finnish paganism which was practised by the Finnish people prior to Christianisation. It has many features shared with fellow Finnic Estonian mythology and its non-Finnic neighbours, the Balts and the Scandinavians...

, are spots where an eternal flame associated with Will o' the wisp

Will o' the wisp

A will-o'-the-wisp or ignis fatuus , also called a "will-o'-wisp", "jack-o'-lantern" , "hinkypunk", "corpse candle", "ghost-light", "spook-light", "fairy light", "friar's lantern", "hobby lantern", "ghost orb", or simply "wisp", is a ghostly light or lights sometimes seen at night or twilight over...

s burns. They are claimed to mark the places where faerie gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 is buried. They are protected by a glamour

Glamour (presentation)

Glamour originally was a magical-occult spell cast on somebody to make them believe that something or somebody was attractive. In the late 19th century terminology a non magical item used to help create a more attractive appearance gradually became 'a glamour'...

 that would prevent anyone finding them by pure chance. However, if one finds a fern seed from a mythical flowering fern

Fern

A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

, the magical properties of that seed will lead the fortunate person to these treasures, in addition to providing one with a glamour of invisibility. Since in reality the fern produces no flower and reproduces via spores under the leaves, the myth specifies that it blooms only extremely rarely.

Although clearly folklore, the claim has been made that the Outokumpu coppermine — the largest coppermine in Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

at its time — was discovered due to some light phenomena or another.