To begin with, there were fire and ice. To the south, the land of the end, present at the very start, Muspellheim. Opposite this was the frozen wasteland of Niflheimr, obscured by banks of fog. Between them lay a vast cosmic expanse of nothingness, known as Ginnungagap.
Within the midst of Niflheimr, there was a bubbling spring, Hvergelmir, its waters tainted by thick, corrosive venom. Hvergelmir debouched into some eleven noxious brooks, the Élivágar, which poured southwards, piling through the mists, before reaching the precipice which marked the end of Niflheim, freezing in the vast emptiness of Ginnungagap.
Eventually, with the building up of banks of ice from the outflow of Hvergelmir, Ginnungagap was narrowed, and a goldilocks zone, warmed by the sparks - primitive stars? - flying up from the broils of Muspellheim, appeared. Within this region, two beings appeared: the first, the father of the jotnar, Ymir; the latter, Auðhumla, a cow, whose milk, ejected to the four directions, fed the giant. Auðhumla sustained herself with salt licked from the blocks of ice on the northern side of the grassless void, eventually freeing other life forms therefrom, including Búri, forebear of the Æesir. Meanwhile, other forms emerged from under the armpits and between the thighs of Ymir - the early jǫtnar.
Some time later and Búri has had a son, Borr, who marries Bestla, the daughter of the giant Bǫlþorn. They have three sons - Óðinn, Vili, Vé - who provide the next stage in cosmic development by killing Ymir and using his dismembered form to refashion the universe in a more inhabitable state. This would, of course, have marked the beginnings of the disagreements between gods and jǫtnar, if not the end of the latter race's primordial forms, were it not for Bergelmir the son of Þrúðgelmir, who survived the inundation caused by the outporing of blood from his slain grandsire aboard his lúðr with his wife to revive the frost giants.
The Norse world tree par excellence is, of course, the famous Yggdrasil (or askr Yggdrasils), which rose from three roots located above and watered by three wells, more on which below. Yggdrasil marks the place where the Æsir meet in council and sit in judgment. Four deer - Dáinn, Dvalinn, Duneyrr and Duraþrór - dwell in the heights of its canopy, eating the foliage they find there, while the fell drake Níðhǫggr gnaws at its roots, causing this most noble of trees untold agonies. Another inhabitant is the squirrel Ratatoskr, who carries messages (mainly of an insulting nature, without doubt) between the proud eagle who sits atop Yggdrasil and the grim Níðhǫggr in the stygian depths of the cosmos.
The eagle may well be one and the same as Hræsvelgr, a jǫtunn in that shape who is the origin of all winds. Between his keen eyes sits Víðópnir, a falcon. These two are said to live atop Mímameiðr, which may thus be identified with Yggdrasil.
A similar name, which appears to reference the wise and mysterious Mímir, is Hoddmímis holt, a small wood where Líf and Lífþrasir hole up to survive Fimbulvetr and Ragnarǫk.
Finally, Læraðr is a tree which stands atop Valhǫll, grazed by the stag Eikþyrnir and the goat Heiðrún.
Onto the wells which bestow liquid refreshment to the great, long-suffering cosmic tree, these are three in number.
Hvergelmir is the primordial spring in the midst of Niflheimr, from which the Élivágar (and, indeed, all waters) have their source. It is fed by liquid falling from the antlers of Eikþyrnir, a hart who dwells in Valhǫll. Within the fount are numerous serpents, including evil-minded Níðhǫggr, scion of the dark mountains of Niðafjöll. Hvergelmir - also known as Vaðgelmir perhaps - was apparently bordered by Nástrǫnd, where murderers, adulterers and oath-breakers were gnawed upon eternally by Níðhǫggr. On Nástrǫnd, there lay a hall whose doors faced north. This too was inhabited by serpents, whose venom dripped constantly from the roof of this forsaken place.
Mímisbrunnr stands in the place where formerly existed the primordial cosmic expanse of Ginnungagap, now the domain of the hrymþursar ("frost-giants"). It takes its name from Mímir, a decapitated god whose head provides Óðinn with counsel. Mímir drinks from it each morning, while Óðinn once sacrificed an eye for the opportunity to benefit from Mímir's wisdom. Also in the vicinity is the Gjallarhorn, whose portentions note sounded by the one-eared Heimdallr will cause the gods to muster for Ragnarǫk.
Urðarbrunnr stands beneath Yggdrasil close to Ásgarðr, in the midst of the land of men, and is presided over by the three greatest Nornir, namely Urðr - the well's namesake - Verðandi and Skuld. Nearby, beneath the boughs of Yggdrasil, lies the plain of Iðavǫllr, upon which the gods gather at moot.
The first rivers are the Élivágar, which run through Niflheimr carrying the highly-toxic primordial substance of eitr. Their names are commonly given as Svǫl, Gunnþrá, Fjǫrm, Fimbulþul, Slíðr (notable for the swords which turn beneth it), Hríð, Sylgr, Ylgr, Við, Leiptr and Gjǫll. The underworld counterpart of Bifrǫst, Gjallarbrú is the point at which the Gjǫll river is crossed on the road to Éljúðnir, the grim hall of Hel in Niflheimr. It is guarded by Móðguðr and marks the end of a nine-day journey through vales as black as pitch. The bridge itself is opulent, being described as thatched with gold. Nearby, there lies Gnipahellir, the cave which serves as a kennel for the hellhound Garmr, guardian of Hel's gate. In this region are the black, sunless waters of Ámsvartnir, a lake in which lies the island of Lyngvi, prison of Fenrir.
Other significant rivers include the Kǫrmt, Ǫrmt and Kerlaugar twain, rivers crossed by Thor as he attends council, and the Ífingr, a river which separates Ásgarðr from Jǫtunheimr, as well as the Vimur river, sometimes described as the largest of the Élivágar, which Þórr had to cross on his way to his encounter with Geirrǫðr. Gjálp, one of Geirröðr's daughters, attempted to cause a flood to drown the god by urinating in the river, but was stymied after Þórr hurled a great rock, which temporarily dammed the stream, and made his way across with the aid of a rowan-tree. Gjálp met her end alongside her sister Greipa in her father's hall, their spines broken by Þórr, having extricated herself from the place he'd left her, beneath the rock.
Ásgarðr is the realm of the Æsir, the most significant of the Norse gods. This vast plain high in the cosmos was chosen by the Æsir as the perfect place to make their home, and it is divided into a number of realms, each reflecting the personalities and spheres of interest of the major deities.
A significant problem with the location was, however, early noted by the gods, who contracted a mysterious master mason to build a defensive wall about Ásgarðr. He claims to be able to finish his work in three winters, demanding the sun, the moon and the hand of Freyja as his price. The gods, to his amazement, agree, with the proviso that he complete the build in one winter. Without further ado, he cracks on, aided by his trusty stallion Svaðilfari.
Well, a short while later, much to the surprise - not to mention chagrin - of the Æsir, the work (in a manner most unlike any major infrastructure projects down here on dreary old Miðgarðr) is proceeding well ahead of schedule, mainly due to the tireless labour of Svaðilfari, who shuttles the monumental building materials required for so big a job with ease.
Desperation begins to take hold, with Óðinn willing to hear any options available to him as he sought to extricate the gods from this ill bargain. Fortunately, the Æsir at that time included amongst their number the crafty Loki. However, the downside would be that this most mercurial of figures might needs some... persuasion if he were to furnish his aid.
In these kinds of circumstances, threats of violence tend to work wonders.
Loki, suitably incentivised, puts his shape-changing abilities to good use, transforming into a mare, with the intention of distracting Svaðilfari from his toil. It works a treat: Svaðilfari desists from his labours in a rather epic manner, tearing away from his tack and making a beeline towards this mysterious stranger at a gallop. Loki, getting much more than he bargained for, ends up not only violated by the long, throbbing ithyphallus of the wild stallion Svaðilfari, but, in another bizarre turn of events, finds himself pregnant. The offspring of this odd couple was Sleipnir, the mighty eight-legged steed of Óðinn.
The mysterious mason, stymied in such dramatic fashion, was seen chasing his horse into a forest. He was eventually unable to complete his task on time due to these circumstances. What is worse, when he was revealed to be a hrimþurs, the gods' previous promise of his safety were rendered invalid: he was quickly dispatched by mighty Þórr with a swing of his own trusty sidekick, the hammer Mjǫllnir.
Thus was Ásgarðr fortified and divided, with many mansions and halls of the gods set among the wondrous plains. Ásgarðr's watchman was Heimdallr, who kept a guard on the shining rainbow bridge of Bifrǫst (or Bilrǫst) from his heavenly mountain castle Himinbjǫrg on the marches of Ásgarðr. Heimdallr's hearing was so keen that he could hear grass or wool grow, and he possessed powers of sight rendering him ideal for his role as watchman of the cosmos. Another odd fact about him was that he was reported to have been born to nine sisters among the jǫtnar!
Those deemed glorious dead, whose doom fell in the midst of battle, were spirited away by the imperious valkyrjur to Ásgarðr, to be separated between Óðinn and Freyja. Half were dispatched to Valhǫll, Óðinn's great feasting-hall, standing in the midst of his royal domain of Glaðsheimr in Iðavǫllr, where the chiefmost Æsir goods meet in grim council. Half were sent to the mead of Fólkvangr, ruled over by Freyja, where they were joined by other souls deemed worthy of this honour. Within Fólkvangr stood Sessrúmnir, Freyja's wide hall, which may well double as the ship which carries those bound for her company to the goddess. Óðinn held other possessions, including silver-roofed Valaskjálf, wherein is the throne of high Hliðskjálf, from whence he can enjoy a view of the whole of the cosmos and observe goings-on however far afield.
Also within Ásgarðr was the land of Þrúðvangr or Þrúðheimr, the domain of Þórr, where he dwelt at his hall Bilskirnir. His beautiful brother Baldr held court at Breiðablik before being so cruelly struck down through the wiles of that tricky fellow Loki. His son Forseti would administer concepts of justice and law from his hall at Glitnir, roofed with silver and borne upon columns of gold. Ullr, meanwhile, prefers the cold setting of Ýdalir, were this archer-god can live surrounded by the yews from which the tools of his trade are made.
Out on the marshes of Ásgarðr stood Fensalir, home of Frigg, highest ranking of all ásynjur and spouse of Óðinn. The other goddesses enjoy the comforts of Vingólf, which too receives some men slain on the field of war. Meanwhile, Njǫrðr, erstwhile lord among the Vanir, was settled on the sea coast at Nóatún, while Sökkvabekkr - the "sunken bank" - is an area of shallow sea where dwells the mysterious prophetess Sága. Nearby is a headland, Nes Ságu. Njǫrðr's son Freyr received Álfheimr, home of the mysterious Ljósálfar, the "Elder Children of Ivaldi," as his own upon the emergence of his first tooth. The Ljósálfar also dwell in other heavenly realms: above Ásgarðr, there lie other heavens. The first of these is Andlàngr, above which can be found Víðbláinn. Víðbláinn holds a mountain called Gimlé, upon which is a great hall, currently inhabited by Ljósálfar, which is vouchsafed for the souls of the righteous. Among the number of the Ljósálfar was Iðunn, keeper of the apples of youth within Ásgarðr, who delighted in the vales close to the woods marking the borders of that realm.
Humankind dwelt in Miðarðr, at the very centre of the cosmos, below Ásgarðr at the lower end of Bifrǫst, and above Niflhel, the land of no return beneath the dank soil. Round about Miðarðr lies the ocean, home of the vast, serpentine Jǫrmunganðr, another of the offspring of wily Loki and his mate Angrboða, with a fence fashioned by Óðinn, Vili and Vé from the eyebrows of the fallen titan Ymir preventing ingress from the perilous realms of the jǫtnar beyond.
Dark, foreboding Myrkviðr lies in the south of Miðgarðr. It marks the boundary between the realm of men and gods on the one hand and that of the terrifying, ancient Surtr - Múspellsheimr - on the other. Okolnir is a plain in this general direction, on which stands a hall, named for Brimir (an alias of Ymir), ever filled with song and laughter, and frothing ale. To the north, approaching Niflheimr, lay the lands of the dvergar, offspring of Sindri, ingenious artificers and covetors of all things gleaming and magical. This place is named Niðavellir, the "dark fields," which are perhaps contiguous with Niðafjöll, from whence sprang Níðhǫggr. A golden hall stands there, home to the sons of Sindri. Singasteinn stands on the shore, the site - or object - of a battle between the inimical gods Loki and Heimdallr in the form of seals.
Other lands on this plain are perhaps Bari or Barey, a lundr or grove in which Freyr consumates his marriage with the giantess Gerðr. The name is suggestive of an island location, and may be part of Vanaheimr, home to the Vanir gods. Beneath the sea, meanwhile, lies the domain of Ægír and his bride Rán, along with their nine wave-daughters.
Beyond Miðarðr, far to the north-east (and even further in the other directions), lies mountainous Jǫtunheimr, home of the jǫtnar. This vast realm is divided into many places and subdomains, each under the sway of local jǫtunn-jarls.
Járnviðr (the "Iron Wood") is a forest located east of Miðgarðr, presumably close to or within the bounds of Jǫtunheimr. It is mentioned in Vǫluspá and Gylfaginning as home to giantesses known as járnviðjur, the most significant of whom, described as an old woman with nefarious powers, is known to bear and nurture giants in the form of wolves. She is very likely to be identified as Angrboða, consort of the trickster Loki, by whom she was the mother of the great wolf Fenrir. Another of the járnviðjur may have been Skaði, who is given this title by Eyvindr Skáldaspillir. Þrymheimr is the home of the powerful jǫtunn Þjazi, father of imperious Skaði, whose downfall would be his overwhelming desire for the blameless Iðunn, mistress of the apples and bestower of eternal youth.
Another forest in Jǫtunheimr is named Gálgviðr ("Gallows Wood"), and is home to Fjalar, a rooster whose call marks the beginning of Ragnarǫk.
Gastropnir is the wall of the domain of Menglǫð. Its gate is guarded by one Fjǫlsviður, who claims to have built it from the limbs of Leirbrimir, likely one and the same as the primordial hrimþurs Ymir.
Hnitbjǫrg - the "clashing mountain" - is a mountain wherein dwells the jǫtunn Suttungr, the son of Gillingr. Suttungr would acquire the famous mead of poetry from the dwarves Fjalarr and Galarr, who followed up their murder of Kvasir by killing Gillingr and his wife. They created the mead from the blood of Kvasir - who was born from the admixture of the saliva of the Æsir and Vanir after their war - and gave it to Suttungr in compensation. Its keeper was Suttungr's daughter Gunnlǫð.
The deathless realm of Glæsisvellir, also known as Ódáinsakr, is a wondrous portion of Jǫtunheimr, which offers recovered youth and health to those fortunate enough to chance upon it. Its ruler was Guðmundr, who is the brother of the powerful chief Geirrǫðr, who fell victim to Þórr along with his daughters.
And, at the utmost ends of Jǫtunheimr, the most frightening realm of all: Útgarðr, the stronghold of a particularly conceptually-frightening group of jǫtnar, whose powers are the very elements of the universe themselves.