Where is Hell exactly?

Hell is not a place so much as a state of being. As such, it doesn't have a physical three dimensional location on a map, such as we would have while on earth. Heaven is the state of eternal blessedness with God, the state of seeing God as He is and being with Him. Hell, on the other hand, is the self-determined state of eternal exclusion from heaven, eternal frustration, eternal pain and suffering, eternal unfulfillment. Heaven and Hell will have a "location" at the end of time when we get our bodies back, until that time, or more specifically, before time ceases to be, everyone in hell is a pure spirit: the bad angels (the devil and other demons) and the damned souls who have rejected God on earth.