Yggdrasil

Yggdrasil's structure, as the Prose Edda describes it, is genuinely cosmological rather than decorative: an ash tree whose branches and roots physically connect the nine worlds of Norse cosmology, one trunk holding the entire structure of the universe together rather than standing beside it as a separate sacred object. The Prose Edda names specific beings tending it, the Norns, who draw water from the Well of Urd at its base to keep it alive, and specific beings gnawing at it, most notably the serpent or dragon Nidhogg at its roots, so the tree in the source text is not a static emblem but the site of ongoing maintenance and ongoing damage, a structure actively held together against forces working to unmake it.

The Well of Urd beneath the tree is also, in the Prose Edda's account, where the Norns cast lots and set the fates of gods and men, tying the tree's physical maintenance directly to the working of fate itself rather than treating the well as a separate, unrelated feature of the cosmological landscape. Among the nine worlds the tree's branches and roots connect, the Prose Edda names Asgard, home of the Aesir gods, and Midgard, the world of humans, alongside realms associated with giants, elves and the dead, so the tree's structural role is not confined to linking two or three principal realms but to holding together the entire nine-part cosmos as a single continuous structure.

Because Yggdrasil sits at the structural centre of the cosmos in the surviving textual sources, chiefly the thirteenth century Prose Edda, it has become one of the most recognizable and most widely adopted symbols of modern Norse and Heathen religious identity, reproduced in reconstructionist and revivalist Heathen practice as a devotional image standing for the whole of the cosmology those movements draw on, in a way comparable to how a small number of other single images, the Taijitu for Daoist cosmology or the Sri Yantra for Shri Vidya, come to stand for an entire cosmological system in compressed visual form.

Modern use of the tree image ranges from serious devotional and reconstructionist practice to purely decorative and popular-culture reproduction with no religious content at all, and this atlas records the symbol's source meaning in the medieval textual tradition without treating every modern use of a tree image as continuous with Heathen religious practice.

Because the Prose Edda is a thirteenth century Christian-era compilation of older material by Snorri Sturluson, historians treat its account of Yggdrasil as the fullest surviving description while remaining cautious about how far it preserves pre-Christian belief unchanged versus how far Snorri's own scholarly framing shaped the text, a source-critical caution this atlas applies to Norse cosmological material generally rather than singling out the tree.