Anyone who has seen Indiana Jones and the Raiders of the Lost Ark has seen a pretty good replica of what the Ark looked like. It was a wooden box covered with gold and it was decorated on top with two small statues of winged cherubs facing each other.
The commentators say that the two cherubs normally faced each other but when the Jewish people were not getting along with God they would be turned away from each other.
Inside the Ark were the two sets of the Ten Commandments -- the broken set inscribed by God, and the second set inscribed by Moses.
The whole structure -- called the Mishkan in Hebrew -- was not a portable synagogue or a museum. It was a tool to be used by the Jewish people individually and as a nation, to connect to God.
When it was completed, the Torah relates that the "clouds of glory" -- a manifestation of God's infinite presence called the Shechina -- would literally rest on the sanctuary as a tangible sign that God was with the Jewish people.
When the sanctuary stood, people would feel holiness in the world in a way we can't begin to understand today. No amount of description can begin to give us a sense of what it would have been like to connect spirituality to God via the <>Mishkan. Today we are like people born blind- no description of site can begin to replace the actual experience.
So central is the Mishkan to Judaism that following the account of the Exodus and Mount Sinai most of the rest of the Five Books are spent describing the construction of the Mishkan, its vessels and the priestly service that took place with in it. So detailed is the description within the Written Law that further description within the Oral Law is not needed in-order-to construct it.
Because we don't have it, only 369 of the 613 commandments are applicable and most of those are negative commandments-"thou shall not." Most of positive commandments are focused on how to use the Mishkan to connect to God. The loss of that structure has tremendous implications for the Jews' (and all of humanity's) ability to relate to God and fulfill their mission as a light to the nations.
The service in both the Mishkan and later theTemple was carried out by the priest, in Hebrew: the Cohanim. The first Cohanim were Moses' brother Aaron and Aaron's sons. This line has continued for 3,300 years until today. Most interesting is the fact that recent genetic analysis of the Y-Chromosomes of hundreds of Cohanim from around the world proves that close to 80% are in fact descended from a common male ancestors more who lived more than 3,000 years ago.3
Even though the Temple service has been discontinued for 2,000 years Cohanim (who often have the last name: Cohen, Kagan, Kahn, Katz or Cowen) are still awarded special honors (ie the first person called up during the weekly Torah reading is a Cohen) in recognition of their unique status and responsibility.
This sanctuary -- which was readily dis-assembled and assembled -- the Jews carried around in the wanderings in the desert for 40 years. For 440 years after they entered the land of Israel, but before they conquered Jerusalem, they assembled it in four different locations. After David became king and made Jerusalem his capital, he planned to build a permanent structure just outside the city, atop Mount Moriah where Abraham had offered Isaac as a sacrifice to God and where Jacob had dreamt of a ladder to heaven. For reason that we will explain later, he did not actualize his plan
Finally, in 832 BCE, his son King Solomon built the first Temple there, and it became the permanent sanctuary until it was destroyed by the Babylonians in 422 BCE. At this time the Ark of the Covenant disappeared never to be seen again.