Zion is the traditional name for the Holy Land. While Christians and Jews regard Jerusalem and Israel as Zion, the Biblical homeland of the Twelve Hebrew Tribes, Rastafarians regard Ethiopia as the Holy Land, the New Jerusalem where the Ark of the Covenant now rests and the holy kingdom of King David has continued for thousands of years.
Ethiopia is likewise regarded as the Garden of Eden, where Adam was created from the dust of Mother Earth and Eve was created from Adam's rib. This is reinforced by many archaeologists' assessment that Africa, particularly in the Horn, is the cradle of civilization.
There is a story within the Kebra Nagast, an ancient Ethiopian text, describing the story of the Ark. This is but a brief summary of a wonderful book published as the Kebra Negast by editor Gerald Hausman.
It all began with the Queen Makeda of Sheba, or Ethiopia, when she traveled to Jerusalem to meet with King Solomon, the head of many disjointed nations in the region. King Solomon, the son of David, is well-known in the Bible for possessing deep, deep wisdom. He is also known to be a womanizer, and with Queen Makeda, he was nothing else.
On the last evening before her departure from Jerusalem, Solomon seduced the Queen of Sheba, giving her a ring and telling her that if she becomes pregnant, to give the ring to the child when he returns so Solomon could be sure of his identity.
The Queen Makeda left soon after and, not surprisingly, discovered that she was pregnant. The Queen gave birth to a boy named Bayna-Lehkem. He was a very inquisitive boy, and at about the age of 12, he began to wonder who his father was. He soon discovered that it was King Solomon of Jerusalem. He was very interested in meeting his father, and after pestering his mother for years, she finally acquiesced and agreed to send him to Jerusalem. Before his departure, Queen Makeda gave the child Solomon's ring, telling him to show it to the King as legitimate claim to his line.
When he reached the city, Bayna-Lehkem immediately went to the palace. When he gained an audience with King Solomon, he noticed that the King looked like a mirror image of himself! Bayna-Lehkem began to describe who he was and to show the ring, but Solomon declared that there was no need for this, as he could tell from his visage that the child was his own son. Solomon stated that Bayna-Lehkem looked more like his own father, King David, and that he would rename his child David for his father.
Prince David remained in Jerusalem, studying and spending time with his father for a long time. However, he soon grew home sick for his mother and homeland, and decided that it was time to return home. King Solomon was deeply grieved about this, as he had hoped that David would inherit the throne from him. But no, David knew it was time to leave. King Solomon then declared that he would agree to have David reign as the King of Ethiopia. He gathered his counselors and proposed that their first sons would accompany David to Ethiopia to be his own counselors. The proposal was readily accepted. David's new counselors were sorrowful that they had to leave their homeland, the Lady Zion, where the Ark was kept. Azarayas, one of David's counselors, was approached in a dream by an Angel of the Lord that proclaimed that he should take the Ark with them to Ethiopia. Azarayas stealthily stole the Ark and the group, including David, fled for Ethiopia. When the theft was discovered, the anger was widespread. Solomon's troops pursued David at full speed. When he finally reached Egypt, and asked the locals if David had passed through. They told him that he had been through 13 days ago. When Solomon heard this, he realized that the only way David would be able to go that fast is if he had the help of God, and realized that it was God's decision for the Ark to go to Ethiopia, and Ethiopia became the New Zion.
This was just as King David had prophesied in the Psalms:
Ethiopia shall stretch her hands to God and He shall receive her with honor and the kings of the earth shall praise God.
From this story, Haile Selassie claimed that he was in the line from King David (hence Root of David), and the Throne of David was continued in Ethiopia.
English journalist Graham Hancock even validates the story of the Ark in Ethiopia in his 1993 book The Sign and the Seal : The Quest for the Lost Ark of the Covenant, stating that the Ark was deposited in Ethiopia in 955 B.C. This is a very long, but interesting book. I encourage you to examine all of his vast research to decide whether this is true.