Bifrost: The Burning Bridge Between Earth and Asgard

Bifrost is the three-colored bridge linking Midgard, the world of humans, to Asgard, home of the gods. It is guarded by Heimdall and will break at Ragnarok. Most scholars take it to be the rainbow.

Bifrost is the bridge that links Midgard, the world of humans, with Asgard, the realm of the gods. In the eddic poems it appears as Bilrost, and Snorri Sturluson's Prose Edda calls it Bifrost. Snorri says the gods built it themselves, that it has three colors, and that it is built with more skill than any other work.

The bridge is guarded by Heimdall, who lives at its end in a hall called Himinbjorg. He needs less sleep than a bird, can see a hundred leagues by night, and can hear grass growing. He holds the horn Gjallarhorn, which he will blow when the end comes. Snorri adds that the red in the bridge is burning fire, which keeps the frost giants and mountain giants from crossing, and that the gods ride over it every day to hold court at the well of Urd.

Strong as it is, Bifrost will not last. At Ragnarok the sons of Muspell will ride across it and it will break beneath them. One poem, Grimnismal, says Thor has to wade through rivers on his way to court instead of using the bridge, apparently because it would burn. Its destruction is one of the signs that the old world is ending.

Most scholars take Bifrost to be the rainbow, which fits its colors and its reach from earth to sky, though some have argued for the Milky Way. For readers of ancient visitor theories, it is a guarded gateway between worlds, with a watchman who can see and hear across huge distances. That reading is modern; the texts present it as the gods' road and a boundary that the enemy will one day cross.