The end of the world
Ragnarok

There shall come a time when three winters flow together without summer between. The sunshine grows dim and the weather dangerous. This is called the Fimbul Winter. Many warnings shall appear of these times.

All humanity shall rise up and fight each other.Man shall fight man, friend against friend, brother against brother. This is the time of the wolf. The powers of destruction gather.
The Midgard Serpent rises frothing from the seas and enters the land.

The Fenris Wolf rips its chains apart and devour all that come in its way.
The huge ship Naglfar is launched with Jotuns aboard and set course for the site of battle.
The fire Jotun Surt comes from Muspelheim with flaming sword, and together with an army of flame warriors and Garm the Hellhound, rushes towards the strife.

Heimdall blows his horn and call gods and humanity to fight these horrific monsters.
What happens next is unclear, with many divergent views. Some say that all gods fall in the battle that follows, and with them, humanity. The sky rips apart and the wolves devour Sun and the Moon. Heimdal and Loke kill each other, likewise Tor and the Midgard Serpent.

Fenris kills Odin, but itself is slayed by Odin's son; Vidar. Frøy marches on Surt, Surt wins and lights the whole world in flames. Yggdrasil the World Tree burns and the remnants of the world sinks into the oceans.

Some say that a few gods will survive. The world is born again, the fields will sow themselves and no-one shall ever again starve. The gods discover once more the golden plates they played with at the beginning of time. A new Tree of the World grows out of the ashes of Yggdrasil, but Nidhogg comes once more flying to rest itself at the new tree's roots. The Vanir survive, as they do not take part in Ragnarok.

Maybe some gods will survive as well. Hod and Balder are in Helheim and live through it all, and Høne is in Vanaheim. Mayhap the good Balder will become the next Odin? Some say also that Heimdal survives, as he was slayed once before but revived, which therefore will happen once more. He is the Eternal Guardian of The World Tree, with nine lives.

Gimle
Gimle is the fairest of all halls, and brighter than the sun. It shall survive the devastation. There the human survivors will gather. Some say that only one pair of humans will live; Liv and Livtrase. There seems to be several heavens, and Gimle lies in in the third one, named Vidblåin. At this point only Light Elves reside there.

Background
These tales of Ragnarok are probably coloured by Christianity's Armageddon/Doomsday-stories, and we find mseveral similar traits between the legends. Therefore we can never really know how the Norse originally felt that the end of the world would be like.

There are many connections between daily life and the coming of Ragnarok. The ship Naglfar is made of nail clippings of the dead. Therefore people must be careful to burn all nail clippings, so they won't enlarge the ship that it may carry more Jotuns to battle.
Vidar manages to kill Fenris due to the shoes he blocks its maw with. These shoes are made of soles that people must save and not throw away.
There are many versions of the Ragnarok times, due to a mix with Christianity.