Areas not inhabited by humans. Also wild and feral animals.
A large portion of recreational travel is motivated by experiencing nature or seeing wildlife. It may include ecotourism, safaris, nature reserves or other questions where the aim is not to meet new cultures, but rather explore the non-human part of the planet.
Questions about non-domestic animals, birds, reptiles, etc also belong under this tag, including both wild animals and feral animals.
Note that there is a separate Stack Exchange (in beta) for The Great Outdoors which may sometimes be better suited for questions about active exploration of nature.