3. Jotunheim
This is the home of the Frost Giants ruled by Loki's father Laufey and it is the only other realm shown in the original film. It is a cold, dark, harsh planet. The name Jotunheim means home (heim) of the giants (jotun). The Frost Giants are not yet confirmed to reappear in The Dark World, but sooner or later Loki will lead the Frost Giants against Asgard.
4. Swartalfheim
This is the home of the Dark Elves ruled by Malekith the Accursed and it is set to appear in The Dark World. Christopher Eccleston will be playing Malekith as pictured above. It has also been confirmed that Adewale Akinnuoye-Agbaje will play Algrim the Strong/Kurse, the strongest of all the Dark Elves. In the comics, Malekith persuaded Algrim to engage Thor in battle. During their battle, Malekith order a seemingly bottomless pit to be opened up beneath them in order to trap Thor. Thor was saved by his hammer but Algrim fell into the lava at the bottom. He later emerged as Kurse, more powerful than before, and obsessed with revenge on Thor. While Thor and Algrim were still in the pit, Malekith seized control of The Casket of Ancient Winters and later shattered it, creating a supernatural winter over all of the Earth. The Casket is currently stored in Odin's Vault but it is quite likely that Malekith will gain control of The Casket at some stage during The Dark World. Interestingly, there have been a few images released of Iron Man 3 that show a snow storm on Earth. Coincidence?