Jötunheim, also known as Jötunheimr, is one of the Nine Realms of the World Tree, home of the ancient race of Jötnar. Jötunheim was founded and named by Bergelmir and his wife, the only Jötnar survivors of Odin's slaughter of their forefather, Ymir. Since then, it has become the sanctuary of the Frost Giants, a home where they could grow and prosper.

Fearing his own prophesied downfall at the hands of the Giants come Ragnarök, Odin and the Aesir began to ruthlessly slaughter them all throughout the Nine-Realms. On the verge of extinction, the Giants retreated back to Jötunheim with the help of Tyr, who did not take part in the killings and instead assisted them in their escape by removing all access to the realm throughout all the nine except the two last ones in Midgard, though the one on Midgard's tallest peak required a sacred rune to activate it. The other one was hidden in the Realm Between Realms and Tyr's Temple needed to be flipped in order to restore it, along with the jeweled eyes that the Giants bestowed to their confidantes.

The guardian of the gates of Jötunheim is Duraþrór the Stag. There is a statue of him keeping the entrance of the Heart of the Mountain in Midgard, where at its peak, is the only gate to the Giants Realm left behind after the Jötnar successfully escaped the Middle Realm. Jötunheim's landscape consists of large mountains so high that their peaks reach above the clouds. The only indoor structure seen so far is a large room built inside a hand-shaped mountain, the highest peak in the Nine Realms. The room is adorned with statues and carvings of Giants, written prophecies in its walls and a mural depicting the story of "Loki." After the withdrawal of all the Giants who had remained in Midgard, Jötunheim became the tomb of the Jötnar race, their corpses littering the mountains as they await the return of their guardian.

Helheim, the realm of the dead, is one of the nine worlds of Norse mythology. Its ruler is Hel, the daughter of Loki. Contrary to popular belief, this is not a dark, inhospitable place where people unworthy of Valhalla dwell after death. In the realm of the goddess Hel dwell those who have had the privilege of living a long and fruitful life. In the quiet halls of Helheim rest honest merchants, good wives, hardworking farmers and craftsmen. The deceased used to be buried with objects with which they came into contact during their lives. It is impossible to leave Helheim because it is surrounded by the Gjöll River flowing from the Hvergelmi well, which is located at the root of the Yggdrasil (World Tree), where the dragon Nidhögg rests. Across the river runs the Gjallarbrú Bridge (literally 'Gjöll Bridge'). Even a god who once entered this realm would not be able to leave, but in the Poetic Eddahe, one can visit it and leave, such as Odin. The gate to the underworld is closed by Thrymgjöll (also Helgrind – Hell's Grid), an impenetrable lattice made by three dwarves. Whoever tries to traverse it, immediately becomes paralyzed. Those who lived the life of a warrior and died a heroic death had the opportunity to get to Valhalla, after being chosen by the Valkyries with the Norna Skuld. However, there are cases when such a person was sent to the realm of Hel (= Helheim) after judging. In Norse mythology, the Christian duality of good and evil is often misinterpreted, which causes the empire of Helheim to be associated with Hell. The entrance to Helheim is guarded by the dog Garm. The whole empire is then watched by the giant Hraesvelg (meaning "eater or swallower of corpses"), who takes the form of an eagle and by flapping his wings creates a cold wind. Jötunheimar are referenced throughout Gylfaginning such as when Gefjun takes four oxen, who were her sons with a Jötunn, out of the Jötunheimar to the North and uses them to plough land out of Sweden, forming Zealand. Jötnar and Gýgjar are also described as living in Jötunheimar such as the father of Night, Narfi and Angrboða, the mother of Fenrir. Beings may also come out from Jötunheimar to interact with others, such as the wright who, with the help of his horse Svaðilfari, builds fortifications for the gods to protect them from Jötnar.

Skáldskaparmál tells of how Loki was once coerced into helping the Jötunn Þjazi abduct Iðunn who carried her Northwards, back to his home in Jötunheimar named Þrymheim r. Using Freyja's fjaðrhamr, Loki became a hawk and flew to Þjazi's home while the Jötunn was away, having rowed out to sea. Upon reaching Iðunn, Loki turned her into a nut and flew away with her in his talons. Þjazi later finds out that Iðunn is gone and he chases after them as an eagle, but is killed as he reached Asgard when he flies into a fire that the Gods made.

Later in Skáldskaparmál, Odin rides to Jötunheimar on Sleipnir where he meets the Jötunn made of stone Hrungnir and wagers that no horse there was as good as his. Angered, Hrungnir chases Odin back to Asgard on his horse Gullfaxi whereupon the Gods invite him to drink with them. Becoming drunk, he boasts that he will perform a number of acts including carrying Valhall to Jötunheimar and abduct both Sif and Freyja. When the gods tired of his bragging, they called for Thor. Hrungnir claimed that as he was unarmed, Thor would gain no honour from killing him and so challenged him to a fight in Jötunheimar, at his home Grjótúnagarðar. Thor later meets him there and kills him with Mjölnir, which on its way to Hrungnir, hits the hone that the jötunn was fighting with, shattering it. One of the pieces flies into Thor's head, becoming stuck. To remove it, he went to the völva Gróa, who began a galdr to loosen it. While she was singing, Thor told her that he had carried her husband Aurvandil as he travelled Southwards out of Jötunheimar and that he would soon be with her. In her excitement, she forgot the galdr and the shard remained lodged in Thor's head.

In regards to Jötunheim, and the Land of the Giants, aka the Nephilim / Rephraim descendants who survived the Titan Wars, their original home was located beneath the Canyon during the Age of Atlantis, but they too, like the Gods had to recolate after it's destruction, and the mountain range bearing Jötunheim's name still is the location where they set up after the destruction of Atlantis, among other places. This primary location is an underground kingdom that is blocked off through the use of the Draco technology that generates extremely high level electromagnetic fields, that could either disable any technology or kill anyone who tried to pass through it. Essentially, an energy barrier. They did this to protect themselves from humans and the other Elven lineages who followed Odin that may still hold a grudge, whilst they plotted their revenge against Thor and Odin and Asgard indirectly. Unlike Asgard, Jötunheim is a cavern city surrounding by mountains, because they are underground world's on Earth so to speak, and Agartha is real.

Through the use of creating artificial suns and light, they can create suited living environments with just the amount of light needed so they do not die of lack of sun. When you hear about underground facilities used in human cloning and genetic experimentation or the use or rare bioweapons, it's always those of Jötunheim behind it. They still live beneath ground, and Malta is another one of the primary locations that acts as an entrance to the underground cities. It is but one of many. In the Biblical texts, it tells you the Earth will open during the End of Days / Ragnarok in which the Sons of Jötunheim and Muspelheim will do battle once again with the Forces of the Light which they rejected, leading to their fall from grace. Their obsession with the forbidden and rejected arts is what caused them to earn disfavor with not only Odin's own people of which they were once loyal to and served, but also Enlil, God of the Dark Elf Tribes of Israel who had forbidden the use of Magic, especially that of energy weapons and systems, which they had become obsessed with trying to preserve, prolong and / or restore their longevity they lost after the destruction of the ancient Elven homes and their 'magics' used to sustain them. This is why they have nothing to lose, for they rejected both the Light and the Dark Elves, in favor of their own design. Death of the Spirit leading to Undeath.