The world was not created from nothing — it was shaped from the body of the primordial giant Ymir by Odin and his brothers. Flesh became earth, blood became sea, and his skull became the sky. At the centre of this universe, the world tree Yggdrasil binds the nine worlds together.
In Norse mythology, the world lies in the middle of the great void Ginnungagap, between the burning Muspelheim in the south and the icy Niflheim in the north. The world was created when Odin, Vili and Vé killed the primordial giant Ymir and shaped the world from his body. The earth was made from his flesh, the seas from his blood, the mountains from his bones and teeth, and the sky from his skull. The celestial vault is held up by four dwarves: Austri, Vestri, Norðri and Suðri.
The gods also created the stars from sparks from Muspelheim and set the sun and moon in fixed paths across the sky. The Sun and Moon each drive their own chariot across the sky, chased by the wolves Sköll and Hati, who will eventually swallow them at Ragnarök. At the edge of the sky sits the giant Hræsvelgr in eagle form, and the wind arises when he beats his wings.
The earth is described as flat and surrounded by sea. At the outermost edge of the sea, the Midgard Serpent encircles the world and bites its own tail. Beyond the world of men lies the realm of the giants, Utgard. Within lies Midgard, which the gods created for humans from Ymir's eyebrows. At the centre lies Ásgarðr, the realm of the gods, where Valhall is found among other things.
In the middle of Ásgarðr stands the world tree Yggdrasil, which stretches its branches over the heavens and its roots down into the underworld. The tree has three roots: one among the Æsir, one among the frost giants, and one above Niflheim, where serpents gnaw at the roots. On Valhöll stand the goat Heiðrún and the stag Eikþyrnir, living off the tree.
From Ásgarðr runs the rainbow bridge Bifröst, guarded by Heimdallr. Another bridge, Gjallarbú, leads to the realm of the dead, Helheim, where Hel rules and the hound Garmr guards the entrance.
In Norse mythology, the world is not created from nothing, but shaped from something that already exists. Creation comes through the slaying of Ymir, and the myths therefore bind creation and destruction closely together. The stories also offer an insight into how people in the Norse age understood the world, the gods and humanity's place in the universe.
Sources: Gylfaginning, Völuspá, Grímnismál and Vafþrúðnismál.