Urdar's Well and Yggdrasil

Yggdrasil, the World Tree, is a tree from Norse mythology that was said to have held the entire world in its branches. Its three roots stretched into three different wells, one of which is known as Urdar's Well.

A trip to the legendary well is less impossible than you may think—you just need to Gamla Uppsala in Sweden. According to a sign at the site, the well was excavated in the early 20th century, dates back to the 1180s, and is thought to have been built together with an old Church. 

The tree it once held is mentioned in Poetic Edda, the 13th-century collection of Old Norse by Snorri Sturluson. If you visit the site today, you sadly won't see any mythological, constantly green tree towering above the burial mounds. There is, however, a stump with some small branches.