He knew that he would be facing an angry crowd, but he entered the 'lion's den' without hesitating.
the club's reputation as a 'den of iniquity' [=a place where immoral or illegal things are done]
He spent most evenings in the 'den' reading and smoking his pipe.
(..) since we always sleep in mine anyway. And until they fix the hole, I figured this area could kind of be like a den/hangout/place where we have dirty sex on top of my hockey equipment. Oh, honey, Lucy's here. Oh, I'm sorry. I should clarify. (..)2010 TvShow: Scrubs Title: Our Thanks Season: 9 Episode 13