A bat is hanging upside down in a closed cave of the Manjanggul site in Jeju, South Korea, November 7, 2015. Manjanggul cave is a 7.4km-long lava tube locally with a multi-level structure. It is one of the largest lava tubes in the world having a main passage with a width of up to 18m and a height of up to 23m. (Photo by Jeon Heon-Kyun/EPA)
