Before the dawn of time and before the world was created in Norse mythology, there was a place called Niflheim. Niflheim is a very dark and cold place, and it consist only of ice, frost and fog. Niflheim was and still is, in the northern region of Ginunngagap. Ginnungagap was a great void, nothing but a vast area of empty space between the northern region and the southern region. To the south of Ginunngagap there is a place called Muspelheim, this is the land of fire, and it is so hot there that it only consist of fire, lava and smoke. In Muspelheim there is a huge giant named Surtr, he is the ruler of this land, but he is not the only being here, this is also the home of the fire demons and fire giants in Norse mythology.
It is said that in Nilfheim at a place called Hvergelmir, is where all the cold rivers are from, and it is said to be the source of the eleven rivers. Hvergelmir was the origin of all existence and the place where every living being will go back. Elivagar “ice waves” are the rivers which existed in Niflheim at the beginning of the world in Norse mythology. They were the streams floating out of Hvergelmir. The water from Elivagar was flowing down the mountains to the plains of Ginnungagap, where it solidified to frost and ice, which gradually formed a very dense layer. That is the reason, why there is very cold in the northern plains.