Antarctica

Antarctica is the Earth's southern-most continent, containing the South Pole and almost entirely covered in ice.

Toaru Majutsu no Index Light Novel Volume SS2
On the second Friday of October, Misaka 19900 was sent to Antarctica, to the Extraterrestrial Chaos Observatory, one of the research organizations part of the Gemstone Mining, to rescue the Gemstone held there. During her periodic progress report, she mentioned that she had met some resistance.

Shinyaku Toaru Majutsu no Index
At some point between late November and early December, before December 3rd, Patricia Birdway accompanied an Academy City sponsored research team to Antarctica. While there, they encountered a parasite, later named Sample Shoggoth, which infested Patricia's body, putting her life at risk.