The frigid ice world of Ilum was one of the most sacred locations of Jedi power in the Republic.
Nearly every Jedi made a pilgrimage there at least once during their training to recieve visions on the Force-rich caves and construct a first lightsaber.
The Jedi temple there was subject to a vicious Separatist attack that might have dealt irreparable damage to the Jedi order had it not been for the timely intervention of Padme Amidala.