Isen VI

Isen VI was an ice planet.

The Twelfth Doctor took Clara there in the 25th century to learn skiing. When they arrived, though, it had been terraformed into a jungle planet. Kano Dollar, the richest human in the time period, had bought Isen VI and was altering it to use for his upcoming wedding.

The Doctor had also picked the planet because the TARDIS had detected a Time Lord beacon coming from there. This was because a Hyperion that Rassilon had imprisoned deep beneath the planet had been released by the terraforming. The Doctor was able to freeze it before it could leave Isen VI, and restored the planet to its original icy state. (COMIC: Terrorformer)