There are few things spoken of in the Bible which were held so sacred and so closely monitored by God than that of the ark of the covenant. When the children of Israel were kept in captivity by the Egyptians and when God chose to miraculously remove them from that captivity, a number of things occurred which are extremely important in one's study of the Old Testament. This was all in fulfillment of the promises God had made to Abraham, his son Isaac and Isaac's son Jacob (later called Israel) as to their being chosen for the purpose of furnishing the lineage to the coming messiah. After many years of little intervention into the physical affairs of man, God chose to use a number of miraculous means to assure this line from faithful Abraham, to be able to fulfill His promises. He miraculously gave Abraham and his wife Sarah, a son (Isaac) in her old age, and used providential guidance to bring Jacob and his family into captivity in Egypt where he had also providentially brought Jacob's son, Joseph into power in that nation.
After Joseph had died and another Pharaoh was in power, the Israelites were made captive and then, God used mighty miracles to cause their release from that captivity. These miracles had been part of God's plan in order to show the Israelites, as well as the rest of the world, that He was God of heaven and earth. Shortly after their escape, God gave Moses the ten commandments engraven in stone and also the large and detailed law of the Old Testament, through Moses.
In their early wanderings, and in connection with their newly established law, God instructed Moses to build a tabernacle. A large tent with two rooms behind veils. Behind the first vail was the Holy place, and beyond the next vail was the Most Holy. Only Aaron and his sons (designated as priests for the congregation) were to use this place to offer their sacrifices. Only Moses was allowed to enter the Most Holy to commune with God and to offer annual sacrifices for himself and for the people. Here is a scripture explaining what was to be placed inside the Most Holy place and instructions given to Moses as to the use of the place.
And they shall make an ark of shittim wood: two cubits and a half shall be the length thereof, and a cubit and a half the breadth thereof, and a cubit and a half the height thereof. And thou shalt overlay it with pure gold, within and without shalt thou overlay it, and shalt make upon it a crown of gold round about. And thou shalt cast four rings of gold for it, and put them in the four corners thereof; and two rings shall be in the one side of it, and two rings in the other side of it. And thou shalt make staves of shittim wood, and overlay them with gold. And thou shalt put the staves into the rings by the sides of the ark, that the ark may be borne with them. The staves shall be in the rings of the ark: they shall not be taken from it. And thou shalt put into the ark the testimony which I shall give thee. And thou shalt make a mercy seat of pure gold: two cubits and a half shall be the length thereof, and a cubit and a half the breadth thereof. And thou shalt make two cherubims of gold, of beaten work shalt thou make them, in the two ends of the mercy seat. And make one cherub on the one end, and the other cherub on the other end: even of the mercy seat shall ye make the cherubims on the two ends thereof. And the cherubims shall stretch forth their wings on high, covering the mercy seat with their wings, and their faces shall look one to another; toward the mercy seat shall the faces of the cherubims be. And thou shalt put the mercy seat above upon the ark; and in the ark thou shalt put the testimony that I shall give thee. And there I will meet with thee, and I will commune with thee from above the mercy seat, from between the two cherubims which are upon the ark of the testimony, of all things which I will give thee in commandment unto the children of Israel. (Exodus 25:10-22 KJV)
According to the ancient Hebrew measurements, a cubit was the length from the elbow to fingertips or approximately 17.5 inches. So the ark was some 44 inches long and about 26 inches both high and wide. Shittim wood, according to historians, was one of the acacia family of trees which reportedly is an exceptional grade of hard wood, resistant to decay. And it was covered inside and out with pure gold. The staves with which the Levites were to carry the ark were also made of the hard shittim wood and overlaid with Gold. No one was to touch the ark, including those who carried it. They were only to lift it by the staves. Inside the ark were the two stone tablets which God gave Moses with the ten commandments upon them, Aaron's rod which budded and a golden pot which held some manna on which the Israelites survived for a long period. The ark was symbolic of the great things God had performed to aid the Israelites.
At one point, the ark was taken by the Philistines when they and Israel's army were at battle. The story of this is quite long but of much interest. It is suggested that the reader, read the account found in First Samuel, chapter 4, chapter 5 and chapter 6. Although Israel was in some disfavor of God at the time, the ark in the hands of the Philistines proved to be a curse upon them and they finally returned the ark to Israel to rid themselves of the misfortunes they were facing. Truly, it is quite fascinating.
Another item of interest is that once when King David was having the ark transported from the house of Abinadab in Gibeah, the two sons of Abinadab, Uzzah and Ahio, drove the cart. And at one point near Nachon's threshing floor, the scriptures say the oxen shook the cart and Uzzah reached up and placed his hand on the ark to stabilize it. God then smote him and he died. 2 Samuel 6:6-7.
King Solomon was permitted to build an edifice for God in Jerusalem, which he did, a temple of splendor and into which was taken the ark of the covenant. The record as shown in 1 Kings, chapter 8, specifies that inside the ark when it was moved into the temple, there were only the two tables of stones.
And, in the book of Jeremiah, the Lord speaking through the prophet said: "And it shall come to pass, when ye be multiplied and increased in the land, in those days, saith the LORD, they shall say no more, The ark of the covenant of the LORD: neither shall it come to mind: neither shall they remember it; neither shall they visit it; neither shall that be done any more". (Jeremiah 3:16 KJV)
So, the once esteemed symbol of God's greatness became a thing of the past. There is no biblical record as to what became of the ark, and no historian furnishes an explanation. We do know that in 586 B.C., the Babylonians destroyed Jerusalem and the temple Solomon had built, and one of the apocryphal books, the Greek 3rd Book of Ezra (1 Esdras 1:54) makes this remark: "...took all the holy vessels of the Lord, both great and small, and the ark of God, and the king's treasures, and carried them away into Babylon."
The Israelites had departed from following the Law of God, given through Moses and had substituted their own traditions and had also entered into idolatry. They were taken into captivity as God had warned over the years, until they were separated from Him.