I agree; I find the idea of Hell as a grave to be more understandable, but I was talking more about the place of punishment.
Place or a condition?
2nd Thess. 2 v 9 equates punishment with everlasting destruction.
So, the biblical 'punishment' is: destruction.
The wicked are: destroyed forever. - Psalm 92 v 7
The word 'Gehenna' has been translated into English as hellfire.
Gehenna was just a garbage pit outside of Jerusalem where things were destroyed and not kept burning forever. So, Gehenna is also a fitting symbol for destruction.