The old song cries out:

 "years I spent in vanity and pride, knowing not my Lord was crucified
knowing not it was for me he died at Calvary. Mercy there was great and grace was free.
Pardon there was multiplied to me. There my burdened soul found liberty at Calvary."

 Another well mourns:

"Were you there when they crucified my Lord" ... "Sometimes it causes me to tremble, tremble, tremble."

What happened at Calvary? It was more than Physical death as agonizing as that was. It began in Gethsemane where He was sore amazed. ( Mark 14:33 And he taketh with him Peter and James and John, and began to be sore amazed, and to be very heavy;) It is difficult for us to fathom the one that spoke galaxies into existence on his face in amazement and perplexity. He was alone. The disciples were asleep. Even God would soon forsake him. What happened between there and a hill called Calvary or Golgotha opened a door through which have passed the host of all the redeemed. What happened?

First there is the obvious. Crucifixion.
From ISBE Vol II pp761

 "Among the Romans crucifixion was preceded by scourging, undoubtedly to hasten impending death. The victim then bore his own cross, or at least the upright beam, to the place of execution;  When he was tied to the cross nothing further was done and he was left to die from starvation. If he was nailed to the cross, (He was!) at least in Judaea, a stupefying drink (He refused it) was given him to deaden the agony. The number of nails used seems to have been indeterminate. A tablet, on which the feet rested or on which the body was partly supported, seems to have been a part of the cross to keep the wounds from tearing through the transfixed members The suffering of death by crucifixion was intense, especially in hot climates. Severe local inflammation, coupled with an insignificant bleeding of the jagged wounds, produced traumatic fever, which was aggravated by the exposure to the heat of the sun, the strained position of the body and insufferable thirst. The wounds swelled about the rough nails and the torn and lacerated tendons and nerves caused excruciating agony. The arteries of the head and stomach were surcharged with blood and a terrific throbbing headache ensued. The mind was confused and filled with anxiety and dread foreboding. The victim of crucifixion literally died a thousand deaths. Tetanus not rarely supervened and the rigors of the attending convulsions would tear at the wounds and add to the burden of pain, till at last the bodily forces were exhausted and the victim sank to unconsciousness and death. The sufferings were so frightful that "even among the raging passions of war pity was sometimes excited"

Listen to the Psalmist describe it in "real time":

Psalm 22:14 - 18
14 I am poured out like water, and all my bones are out of joint: my heart is like wax; it is melted in the midst of my bowels.
15 My strength is dried up like a potsherd; and my tongue cleaveth to my jaws; and thou hast brought me into the dust of death.
16 For dogs have compassed me: the assembly of the wicked have inclosed me: they pierced my hands and my feet.
17 I may tell all my bones: they look and stare upon me.

Psalm 129:3 The plowers plowed upon my back: they made long their furrows.

Isaiah 52:14 As many were astonied at thee; his visage was so marred more than any man, and his form more than the sons of men:

Then there was the Shame

Hebrews 12:2 Looking unto Jesus the author and finisher of our faith; who for the joy that was set before him endured the cross, despising the shame, and is set down at the right hand of the throne of God.

Why do we assume that crucifixion, naked, in the presence of those he loved, for crimes he did not commit, did not carry with it a stigma of shame greater than that of any other man. They accused him of the greatest crime - Blasphemy! Did he despise the shame? Would you have? Wasn't he the sinless one? Was he not God manifest in the flesh. Can you grasp the magnitude of that act? If you were caught in some despicable act, and the facts were made public, it would cause you shame.

Then there was Separation.

But was that all? I think not. There was his separation from his father. That says more than it appears to say. Imagine the trinity, together from eternity past (who can understand that?) Perhaps back then God was all together in Himself. I don't pretend to know. I know Paul speaks of this in 1Corinthians 15:28.

" And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all."

Was it always so? One cannot know for sure, but what we can know is that somewhere on that cross, God the Father forsook his Son. That was the first and only time that would ever happen. He died alone. The Psalmist again gives it to us in real time.

Psalm 22:6 But I am a worm, and no man; a reproach of men, and despised of the people.

Psalm 22:1 My God, my God, why hast thou forsaken me? why art thou so far from helping me, and from the words of my roaring?

There was the Sorrow

Isaiah 53:3 He is despised and rejected of men; a man of sorrows, and acquainted with grief: and we hid as it were our faces from him; he was despised, and we esteemed him not.

Lamentations 1:12 Is it nothing to you, all ye that pass by? behold, and see if there be any sorrow like unto my sorrow, which is done unto me, wherewith the LORD hath afflicted me in the day of his fierce anger.

Psalm 69:20 Reproach hath broken my heart; and I am full of heaviness: and I looked for some to take pity, but there was none; and for comforters, but I found none.

Can we think of anyone who sweat as it were great drops of blood in his amazement? Forsaken of God and afflicted of God, he has none to comfort him, or pity him.

BUT, are the items above all the the suffering involved?  Which could we say was the most difficult to bear. Take off the shoes of your heart. We are on holy ground. Does this one not stagger the mind? Can we understand?

He Became Sin.

John 3:14,15  And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up: That whosoever believeth in him should not perish, but have eternal life.

There is the mystery. A serpent on a brass pole. Brass, the metal symbolizing judgment. But what does the serpent tell us. Lucifer was the serpent in the garden that deceived Eve. He is unrelentingly evil and hates you. He seeks your eternal destruction in Hell. Jesus Christ became all the ugliness of the serpent on the brass pole. He not only took your sins in his own body, but literally became sin for us. The holy one of Israel! It is beyond us. We cannot comprehend it. We fall on our faces in horror and then realize he became sin for us that we might be made into his very righteousness.

2Corinthians 5:21 For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.

Hallelujah, what a saviour.

What is hindering you right now from bowing your head in awe, recognizing your own vile sinfulness, and, by simple faith, ask him to save you and bring you into his family. Call on him in full understanding that what he did, he did to bring you into his life, and give (yes GIVE!) you his righteousness.

Christian, will you bow your head and give him back your heart?

Now I've given to Jesus everything
Now I gladly own him as my king
Now my raptured soul can only sing
Of Calvary.

Mercy there was great and grace was free
Pardon there was multiplied to me
There my burdened soul found liberty