The Dalek Asylum was a snowy and mountainous planet used by the Daleks as a prison and a "dumping ground" for Daleks who had malfunctioned, gone insane and/or become mentally scarred by battles.
After the Alaska crashed on the planet, the Parliament of the Daleks feared the malfunctioned Dalek inmates could escape. In order to destroy the planet and the Daleks inhabiting it, they kidnapped the Doctor, Amy Pond, and Rory Williams, and sent them to the surface in order to deactivate the planet's defences.
After doing so, the Doctor and his companions managed to use a transporter to escape to the TARDIS on board the Dalek ship before the Asylum was destroyed.(DW: Asylum of the Daleks)
