After the Babylonians conquered the Israelites, the Ark of the covenant vanished from history.
Many, if not all religions, treasure relics. But it can be safely argued that no religious object (besides the Holy Grail, perhaps) has had an impact in popular culture as significant as that of the Ark of the Covenant.
Exodus 25 explains the Ark was to contain the tablets of the covenant law; namely, the Ten Commandments:
Now, after this first mention, the Ark only sporadically appears in the Bible, never to be mentioned again in the Old Testament after 2 Chronicles 35 (Josiah tells the Levites to “put the sacred ark in the temple that Solomon son of David king of Israel built”). It is mentioned once in Paul’s Letter to the Hebrews:
Behind the second curtain was a tent called the holy of holies. In it stood the golden altar of incense and the ark of the covenant overlaid on all sides with gold, in which there were a golden urn holding the manna, and Aaron’s rod that budded, and the tablets of the covenant; above it were the cherubim of glory overshadowing the mercy seat. Of these things we cannot speak now in detail.
And then one final time in the book of Revelation:
Then God’s temple in heaven was opened, and the ark of his covenant was seen within his temple; and there were flashes of lightning, loud noises, peals of thunder, an earthquake, and heavy hail.
The contents of the Ark that Paul enumerates (Aaron’s rod, the manna, and the tablets) have been interpreted by the Church Fathers as pointing at Jesus Christ, the rod representing Jesus’ eternal priestly authority, the manna being a prefiguration of the Holy Eucharist, and the tablets of the Law as announcing the Lawgiver himself. For some, this explains why the Ark is nowhere to be found: it would be no longer a relic, but a person.
The Ethiopian Ark
The Babylonian Empire conquered the Israelites by the end of the 6th century BC. The Ark, at the time supposedly kept in the Temple in Jerusalem, has vanished from history since. Whether it was destroyed, captured, or hidden, nobody knows.
Some Christian Coptic traditions claim that just before the Babylonians sacked Jerusalem, the Ark found its way to Ethiopia. According to that very same tradition, the Queen of Sheba (whose visit to Solomon’s palace is noted in Scripture and celebrated in art) and King Solomon had a son: Menelik I, the founder of a dynasty of Solomonic emperors who, for three thousand years, ruled Ethiopia. He, Menelik, would have personally overseen the moving of the precious chest to where it still (allegedly) resides: the Ethiopian town of Aksum. More specifically, the Ark was preserved in the Cathedral of St. Mary of Zion.
Church authorities say only one man, the guardian of the Ark, Abba Gebre Meskel, is allowed to see the Tabot (as the Tablets are called in Ethiopia), and they have never permitted it to be studied for authenticity. Only the monks in charge of taking care of the site may enter, and very few are even allowed to speak to them.
Under the Temple?
Temples in the Ancient Near East had designated spaces for sacred religious objects which were considered the property of the deity worshipped. As the popular speaker and biblical scholar Tom Meyer explains, the Temple in Jerusalem might have had such designated areas, hidden from the public eye.
As he told Express, “it was in secret chambers like these, whose whereabouts were guarded by a select few, that the Ark of the Covenant could have been hidden before the final Babylonian invasion of Judah in 586 BC, which culminated with the destruction of Jerusalem and the Temple of Solomon.”
In fact, the Bible lists the many treasures plundered and carried to Babylon by the King Nebuchadnezzar, not mentioning the Ark of the Covenant. This omission suggests it may have never been stolen after all. And when the plundered treasures (some 5000 objects, according to some accounts) were sent back to Jerusalem by King Cyrus and restored to the Second Temple, the Ark is not mentioned either.
It may be then that the Ark was put in one of these chambers under the Temple, especially considering there is historical precedent for putting religious relics in underground chambers, and that there may be one such chamber underneath Temple Mount.