(I apologize in advance for the long response
The original intention of Hell was for Satan and his demons. Satan caused mankind to rebel against God, in the bible it is described that before we were saved we were 'children of Satan'. All of us before being saved by Christ are bound for hell. A lot of people can't get their heads around the fact that the heart of mankind is actually quite evil. They think that God is cruel for sending us to hell. But think of it in this perspective: God is actually gracious for allowing sinners into heaven.
If you saw a glass of clean, cool water, and then saw someone drop just a drop of poison into the glass, would you want to drink it?
Likewise, Heaven is so insanely pure that God cannot risk it getting tainted by evil. The penalty for our sins, as trivial as it may seem, is unfortunately death. God, in his divine purity, cannot be in the presence of sin. Hell, in its essence, is the absence of God: The Bible says that everything good comes from God, so Hell is the opposite of all that is good.
Sin's penalty is that blood needs to be shed. Who on earth is pure enough to qualify as a perfect sacrifice for mankind? That's why Christ needed to come down and do it.