In Norse mythology, the World Tree refers to an immerse tree whose branches composed the world. It is also known as the Yggdrasil. ”Ygg” means “to terrify”, it is one of Odin’s many names; while “drasil” means “horse”, in combination “Yggdrasil” is “Odin’s horse”. Odin once hung himself from a branch of this tree, pierced himself with his spear Gungnir, and then discovered the runes. Odin refers to this as “horse-riding”, which is also why the World Tree is named Yggdrasil.
The World Tree was a skyscraping Chinese ash. It connected nine realms.
In Norse mythology, the world supported by Yggdrasil divided into nine realms of three tiers, which are roughly listed below. But in fact there is more than one theory about what nine realms are, as the correct material has been lost.
Asgard: where the Aesir lived. The largest castle here was Odin’s Golden Palace. The Valhalla was also located here.
Asgard was part of the human world which was located in a branch of Yggdrasil, but Snorri Sturluson relocated it to the paradise and connected it to Midgard by the Bifrost. Brave soldiers went to Asgard when they fell. Asgard was the home to the Aesir, and the most deities in Norse pantheon had fought the other deities called the Vanir. But later they achieved peace and maintained it by exchanging hostages. Therefore, Vanirs also lived in Asgard despite that it was the home to the Aesir, and there were Aesirs in Vanaheim too.
The most famous deities in Norse pantheon were Aesirs who lived in Asgard: Odin, Thor and Baldr. Asgard was described as a lofty city in the air surrounded by a long wall. Odin’s hall Valhalla was located in Asgard, and so might be his throne. However, some place or something named Hlidskjalf was also mentioned in Norse mythology, from there Odin could see everything that happened in the cosmos. But currently it is not clear whether it was his palace (other than Valhalla) or his throne.
Vanaheim: where the Vanir lived. The growth and reproduction of all things in the world, the oceans and the wind were all controlled by the Vanir. They even knew many mysterious incantations that Odin did not know.
Vanaheim was where the hall of Freyja (the goddess of fertility and wisdom) located. The Vanir was a group of deities different from the Aesir. There is some evidence that Vanaheim might be a world not so neat and elaborate as Asgard, however, any information regarding Vanir and Vanaheim lacks existing proofs.
Vanaheim was the home to the Vanir, another group of Norse deities who were associated with fertility and magic. There was a war between the Aesir and the Vanir, but the exact reason is unknown. The war might break out as a result of what the Vanir had done that the Aesir could not accept, such as incest and the practice of a magic dishonorable in the eyes of the Aesir. Whatever the cause of war was, a treaty of peace was finally reached. And as the hostages in exchange, Vanir sea god Njord and his two children Freyr and Frejya went to Asgard.
There is no given description of Vanaheim, but it is believed to be a fertile and pleasant realm full of magic and brightness. ”The Vanir was in particular associated to the goddess of fertility, they were required when harvest, sunshine, rain and wind, particularly agricultural population, as well as favorable weather for sailors and fishmen were needed.” Freyja, one of the most popular Norse deities, ruled her kingdom of death Folkvangr somewhere in Asgard. This was a place which might be as pleasant as her home Vanaheim.
Alfheim: where the elves lived. Elves looked very beautiful and were of great magic. They were nice and kind little supernatural beings who took care of flowers and plants and loved the brightness.
Alfheim was also in the paradise and not far from Asgard. It was the home to the Light Elves and all the other elves after Snorri Sturluson. It was rule by Vanir god Frey, one of the hostages sent from Vanaheim to Asgard after the Aesir-Vanir war. Elves were magical creatures that were bright, beautiful and inspired at art, music and creativity.
Professor John Lindow (and others) pointed out, Alfheim was a geographical location between Gota River and Glom River at the Norway–Sweden border, and people in this area were believed to be more “fair” than people in many other places. Therefore, it is believed that the Alfheim in Norse mythology was inspired by this area, but this theory has been challenged. There is no clear description of this realm in Nordic literature, but elves have been thought to be lovely for their good nature.
The Middle World/Middle Yard (Midgard): where human lived. There was a tricolor rainbow bridge constituted of ice, fire and air, the Bifrost, connecting it to Asgard.
Midgard, or Earth, was located in the center of universe below Asgard. It was the home of human and the only realm in the visible world. All the other realms were invisible, despite that they could interact with the visible dimensions occasionally. A burning rainbow bridge named Bifrost or Ásbrú (Old Norse “Aesir’s bridge”) connected Midgard to Asgard.
Ask and Embla was the first human beings living in this human realm, all the other human were their descendants. After Odin, Veli and Ve killed Ymir and created the world, they walked along the coast and found two trees: an ash tree and an elm tree. They created the first man from the ash tree and the first woman from the elm tree. However, they also knew that these little creatures were helpless and easy preys for the jotnar, so they created Midgard to offer them shelter.
After human were created, the deities defended Asgard with high wall. And it was assumed that they created animals in Midgard and on the Bifrost.
Jotunnheim: where the jotnar (giants) lived. The guidepost between human world (Midgard) and giant world (Jotunnheim) was a horrible “iron forest”; it is also said that the “giant world” was beyond the ocean.
Jotunnheim, also known as Utgard, was the land of jotnar (giants). It was the wilderness surrounding Midgard, and a place of forests, mountains and harsh landscape. “Utgard” meant “beyond the enclosure”. It symbolized wildness, chaos, disorder and the place or concept off-grade. Jotuun was a powerful creature. They always fought for chaos and continued to do so after crossing the Bifrost.
Jotunheim (sometimes called Utgard) was the kingdom of jotnar and frost giants near Asgard and Midgard. Jotunheim/Utgard is believed to be out of order and a primitive place of chaos, magic and wilderness. Loki, the god of tricks, was born in Jotunnheim but lived in Asgard. Jotunnheim was considered best to avoid, but there were some stories involving some Asgardian deities who purposefully traveled there.
Jotunnheim and Asgard were separated by a river which had never been frozen and was difficult to cross. But Odin had been to the Mimisbrunnr in Jotunnheim, and Thor had been to Utgard, the stronghold of Utgard-Loki. In the story of Thor and Utgard-Loki, any thing could happen on anyone in Jotunnheim: in his journey, Thor did not have any experience of what it looked like, and in the end of story the stronghold and everyone inside disappeared.
Svartalfheim: where the dwarves lived. Dwarves were great craftsmen of mysterious power and profound knowledge, and they could make many sacred weapons.
Svartalfheim was the home to dwarves who lived under the rocks, in the caves or underground. Hreidmar was the king of Svartalfheim, which was also known as Nidavellir (“dark fields”). Nidavellir / Svartalfheim was located deep down Midgard (earth), and was the home of dwarves who worked hard in smithing. In was a dark and smoky place, where only the fire for smithing and the lit torches on the wall could be seen.
Dwarves were related to crafts and magics. They made Thor’s hammer Mjölnir and Odin’s spear Gungnir, as well as Frey’s ship Skidbladnir which could be folded and put in the pocket. They also helped Odin to steal poems from jotnar and gave them to the deities, who then inspired poets to create their own poems with beverage.
Helheim: the realm shared the same name with Hel, also translated as “Hel”. It was a cold and foggy place without daylight where only the dead could be.
The Norse people believed Helheim to be underground. And it took a long walk on bumpy road in northmost cold and darkness for nine days and nine nights to get there. The gate of Helheim was extremely far from human world. It took the messenger of deities Hermod nine days and nine nights riding Odin’s eight-foot Sleipnir to arrive at the Gjoll River. This river was the border of Helheim, and a crystal bridge Gjallarbru lifted up by a hair spanned the river. The bridge was guarded by a ferocious living dead Modgud (“Furious Battler”), who asked for the name and business of visitors. The souls of the newly dead mostly crossed the bridge by horse or carriage which would be burnt together with corpses during the cremation. The Nordics usually put on a pair of very sturdy boots for the dead so as to deal with the nine days and nine nights of walking on bumpy road to the Helheim. This pair of boots are called “Hel’s boots”.
Niflheim: a world of ice and snow no different from Helheim.
In Norse mythology, Niflheim (from Old Norse Niflheimr, “World of Fog”) was one of the nine realms and full of dense fog and coldness throughout the year. In Medieval German, the people who lived in Nibelheim (Niflheim) was called the Nibelung, which meant people living in the World of Fog.
When the universe was created, Niflheim was located at the north end of Ginnungagap. Muspelheim, the realm of fire, was just across the Ginnungagap from Niflheim. Sometimes, Niflheim was also called the Niflhel, which meant “Home of Hel”, or “hell”. It was a world ruled by Hel, Loki’s daughter, and only the souls of the dead came here. There was no clear difference between Niflheim and Helheim.
Niflheim also meant “Home of Mist” in Old Norse. Hvergelmir, the oldest well and the headwaters of 11 rivers in Norse cosmology, was located here. A hart called Eikthyrnir feasted on Valhalla, and water fell from his horns into Hvergelmir, where all rivers were fed from. There were also countless serpents in the well of Hvergelmir. This well was guarded by Nidhogg, a dragon or serpent, and also a scary creature that gnawed the root of Yggdrasil.
Muspelheim (the World of Fire): an extremely hot realm to the south of Ginnungagap and ruled by jotunn Surtr.
According to Snorri Sturluson, Muspelheim was the primordial world of fire, which played an important role in the creation of universe. Fire giant Surtr lived in this realm, and he would appear during the events of Ragnarok to destroy Asgard and everything else. However, modern scholars did not agree with the interpretation of Snorri Sturluson, instead, they thought Surtr was a giant from this hot world and his only role in primitive Norse mythology was that he played during the Ragnarok.