The home of particular types of wild animal. (Cambridge Dictionary)
The lair or shelter of a wild animal, especially a predatory mammal. (Dictionary.com
A room, often secluded, in a house or apartment, designed to provide a quiet, comfortable, and informal atmosphere for conversation, reading, writing, etc. (Dictionary.com)
A cave used as a place of shelter or concealment. (Dictionary.com)
The lair of a wild usually predatory animal. (Merriam – Webster)
Puffin in den
Moss Den. Dovey Valley. Wales
Gray wolf den.