the lion's den

US /ðə ˈlaɪənz dɛn/
UK /ðə ˈlaɪənz dɛn/
"the lion's den" picture
1.

a place or situation of great danger or hostility

:
He bravely walked into the lion's den to confront his accusers.
Presenting his controversial ideas to the board felt like stepping into the lion's den.