Actually, the Bible does not tell us where Hell is located. In 2 Pet. 2:4, the statement, “cast them into hell,” has been translated by some as “cast down to hell,” but the Greek actually means, “cast into tartarus,” a place of torment and confinement. Others have sought to use Eph. 4:9, “(Now this expression, “He ascended,” what does it mean except that He also had descended into the lower parts of the earth?” to indicate that hell was in the center of the earth, but this is questionable because the passage is talking about the grave, not hell. Compare the comment below from the Bible Knowledge Commentary.
4:9-10. Verses 9-11 serve as a commentary on two words of the quotation in verse 8, namely, ascended (vv. 9-10) and “gave” (v. 11). In verses 9-10 Paul commented on the words He ascended. These two verses are parenthetical in thought because the issue of the passage is the giving of gifts. Before Christ could ascend He had to descend. What is meant by to the lower, earthly regions, literally, “into the lower parts of earth”? The genitive “of” can be taken in three ways: (1) “Into the lower parts, namely, the earth” (a genitive of apposition). This would refer to Christ’s incarnation, His “descent” to the earth. (2) “Into the parts lower than the earth” (a genitive of comparison). This would mean that Christ descended into hades between His death and resurrection. (3) “Into the lower parts which belong to the earth” (a genitive of possession). This would refer to Christ’s death and His burial in the grave. The third view best fits the context because in His death Christ had victory over sin and redeemed those who would be given as “gifts” to the church.
In essence, we can simply know that hell, both the temporary location of all unbelievers until the Great White Throne Judgment of Rev. 20, and the final place called the lake of fire are somewhere in God’s boundless universe.