Bifrost

Bifrost is the shimmering rainbow bridge that the gods built from earth to the heavens, linking Midgard to Asgard. The Prose Edda says it has three colours, that the red in it is burning fire, and that it was made with more skill than any other work, yet it is doomed. Heimdall guards it from his hall Himinbjorg at its end, watching for giants with eyes that see a hundred leagues and ears that hear the grass grow. The gods ride over it every day to their court at Urd's Well, while Thor wades the rivers instead. At Ragnarok it breaks under the sons of Muspell.