Yakutsk, located in Yakutia, a republic in Siberia, is the world's coldest city. In January the mean temperature hovers around minus 40 F, but days in the negative 70s are not unheard of. At this level of coldness, it's best not to wear glasses outside—the metal freezes and sticks to your face, making it difficult to remove your specs without tearing off chunks of cheek.