Caves originate over very long time periods and are very diverse in extent, configuration and character, some dry, others permanently or seasonally wet, others warm, deoxygenated and variously lit at cave entrances. They occur throughout Europe but are most extensive in karstic areas. The flora and fauna are specialised, adapted to often extreme environmental conditions and include some remarkable troglophiles or distinctive roosting or seasonally dormant creatures.

[This habitat could not be formally defined in the expert system because it is not based on vegetation.]