Is Hell in the Old Testament?

What is hell? Hell is simply the netherworld. When the word 'hell' is used it is commonly a reference to Gehenna (lit. valley of muffled cries), which is a part of hell. Gehenna was a valley outside of Jerusalem used for the worship of Molech, this worship being child sacrfice through fire (Lev. xx. 2). Christ uses "Gehenna" as the word for everlasting punishement (Mat. v. 22, etc.) because of its relation to the valley. If one merits his way into everlasting punishement, the damned are like the children being burned by their fathers. God will be the Father burning those who are wicked. This valley was also a supposed garbage heap which was perpetually on fire, another comparison to the place of everlasting damnation. For the wicked are like trash (Mat. vii. 19), thus making them worthy of being thrown into the fire. Gehenna is mentioned in the book of Ben Sirach chapter vii: 

          ...for the vengeance on the flesh of the ungodly is fire and worms.

In the Gospel of Mark chapter ix, something very similar to this is written:

          Where their worm dieth not, and the fire is not extinguished.

With this, we can see hell is clrealy mentioned in the Old Testament.