Antarctica on Mortal Engines world map.
Antartica is the Southern-most continent on the planet. It is covered in ice and snow and rock. It is never visited in the story. However, it is apparently the home of Oil-Drilling Cities. Tom and Hester visited Antarctica in the Jenny Haniver between Mortal Engines and Predator's Gold and aparently made a fortune (which they lost to air pirates). It is likely to also be the home of Ice Cities.