Hebrews 9:11-12
But when Christ appeared as a high priest of the good things that have come, then through the greater and more perfect tent (not made with hands, that is, not of this creation) he entered once for all into the holy places, not by means of the blood of goats and calves but by means of his own blood, thus securing an eternal redemption.

There is a theory that has circulated for many years. It states that the Ark of the Covenant was hidden in a system of caves, under the ground just outside the city of Jerusalem. This theory goes on to say that when Jesus died on Golgotha, a hill just beyond the city wall, the earth quaked, opening a crack in the ground that allowed His blood to trickle down into a hidden cave and drop onto the lid of the Ark, thus following the Old Testament pattern of the High Priest and offering the atoning sacrifice.

On the surface, this theory seems intriguing. But it is very unlikely that the Ark would have been hidden in such a place, and even if that were true, it was not necessary for Jesus' blood to be offered on the Mercy Seat. You see, when Jesus died He offered the sacrifice of his own blood in the very presence of God. He didn't need to go to the temple in Jerusalem to commune with God; His sinless perfection allowed him to have direct access to the very throne of God itself.

The Mercy Seat was not the proper place for Jesus to offer the sacrifice of His blood. It was merely an earthly copy, a foreshadowing of what God was to accomplish through Christ. Before Christ appeared, the High Priest had to sprinkle the blood of goats and calves on the Mercy Seat -- it was never his own blood, for the blood of a sinner can never provide atonement for sin.  

The truest meaning of the mercy seat is that it pointed to the perfect atoning work that Christ would accomplish. Christ, having perfectly obeyed the law of God, served as the mediator between holy God and sinful man, and His life and death satisfied the wrath of God. Because of this, the throne of grace is no longer reserved for High Priests, but all those who place their faith in Christ become part of the "holy priesthood" [1 Peter 2:5] and can now “with confidence draw near to the throne of grace, that we may receive mercy and find grace to help in time of need." [Hebrews 4:16]