Most pet cats will become timid or defensive when outdoors, but not Millie – after being adopted by her mountain-climbing owner Craig Armstrong, Millie has become a feline hiking and mountain-climbing legend.

Located in East Java, Indonesia, Kawah Ijen is a volcano is home to the largest acidic crater lake in the world. What turns the waters of the lake in the 1 km caldera its beautiful turquoise color are the highly sulfuric gases emitted from the volcano underneath.

Undated David Yarrow handout photo of a gorilla as the self-taught wildlife photographer promotes his book, Encounter. (Photo by David Yarrow/Clearview/PA Wire)

A photographer takes pictures as the sun rises over the city of Kronberg near Frankfurt, Germany, Monday, November 4, 2024. (Photo by Michael Probst/AP Photo)

The Aurora Borealis (Northern Lights) is seen over the sky near Inari in Lapland, Finland on February 14, 2019. (Photo by Alexander Kuznetsov/Reuters)

Retired Mongolian-born “yokozuna” wrestler Hakuho (far L), who now goes by the name Miyagino, watches as participants (R) try to push out Japanese wrestler Hakuoho (C) during a sumo class for youngsters on the sidelines of the 14th Hakuho Cup, a competition for young sumo wrestlers from elementary and middle school, at the Kokugikan arena in the Ryogoku area of Tokyo on February 12, 2024. (Photo by Richard A. Brooks/AFP Photo)

Young Haitian migrants hang out in the Batey La Lima community, an impoverished community surrounded by a massive sugarcane plantation in the coastal city of La Romana, Dominican Republic, Wednesday, November 17, 2021. As the rest of the world closes its doors to Haitian migrants, the country that shares an island with Haiti also is cracking down in a way that human rights activists say hasn’t been seen in decades. (Photo by Matias Delacroix/AP Photo)

Icelandic stallions eat hay from a box at a stud farm in Wehrheim near Frankfurt, Germany, Wednesday, March 2, 2022. (Photo by Michael Probst/AP Photo)