Niflheim literally means “The Home of Mists”. In the norse mythology and cosmology this realm is depicted as being very cold, covered by snow, frost and ice. Niflheim is one of the two worlds that collided in the beginning of time, thus creating all the other worlds and life itself. Niflheim collided with Muspelheim – frost and fire.
As I have mentioned before, we speak of worlds not as actually seperate worlds but realms, nine realms of the norse cosmology, so vast that led people to believe (spirit-workers and shamans of old) that the nine realms were actually worlds because of the vastness of the landscape and the different types of weather, flora and fauna that exist in each of the nine realms.
Niflheim is a very ancient world/realm, and its glaciers and mountains were solidified long ago, duo to its famous river, the River Elivagar (Icy Waves). This great river crystallized all things into frost, this everything turned into ice and remained as such. When muspelheim collided with Niflheim, the ice of Niflheim began to melt away in the southernmost areas. It was when the first being was created/came to life, the great frost giant Ymir, born of ice and fire unified.
Unlike the other realms of the norse cosmology, its very hard to be aware of the seasonal changes in Niflheim, it seems to be always winter, similar to the artic regions of out own world. The days are long and the nights longer still at Winter, it seems that night never ends.
More than half of Niflheim is covered by snow and ice, and it will never melt. The weather is often cloudy and shrouded in mist on the low land. The sky is covered most of the time, so it is easy to get lost in here, the stars or the position of the sun and moon are of no avail, and everything in the landscape looks exactly the same thousands of miles in every direction. Closer to Svartalfheim the landscape turns more mountainous and the ice starts to melt by the shore, creating a sea of icebergs and snow-covered islands till it reaches the southern shores of Svartalfheim.
The most important geographical feature in Niflheim, is probably the sacred well named Hvergelmir. Hvergelmir is the largest well sacred well, and hot-spring of turbulent waters from which many rivers flow.
About the fauna and flore of Niflheim, those only exist in the northernmost parts near Svartalfheim. A few plants dotted the soils of the islands and the tundras. In the water there are seals and other cold-water mammals. There are also a few mammoths roaming in the tundras and a dire wolves to the north-east.