The Cloud Peak Mine was a mountain site located on Third Earth that was rich in deposits of Thundrillium.
After the awakening of Mumm-Ra, his armies of Lizards used advanced technology to fuel their conquests. This technology, however, needed to be powered by Thunderillium and thus a mining operation was conducted at Cloud Peak Mine that was excavated by the Driller along with Lizards and overseen by Grune. The amount of the mineral assembled was enough to power Mumm-Ra's army for centuries.
When the ThunderTank was low on power, Panthro decided to raid the Cloud Peak Mine in order to gather some Thunderillium. Thus, he was accompanied by Lion-O and his comrades on this mission. Their battle against Grune's forces led to a collapse in the mine but not before Cheetara gathered a small amount of Thunderillium to power the ThunderTank.