The modern city of Aksum is located in the northeastern portion of what is now Ethiopia, on the horn of Africa. It lies high on a plateau 7200 ft above sea level, and in its heyday, its region of influence included both sides of the Red Sea. An early text shows that trade on the Red Sea coast was active as early as 1st century BC. During the first century AD, Aksum began a rapid rise to prominence, trading its agricultural resources and its gold and ivory through the port of Adulis into the Red Sea trade network and thence to the Roman Empire.
One reason we know what we do about Aksum is the importance placed on written documents by its rulers, particularly Ezana or Aezianas. In the early 4th century AD, Ezana spread his realm north and east, conquering the Nile Valley realm of Meroe and becoming ruler over part of both Asia and Africa. He constructed much of the monumental architecture of Aksum, including a reported 100 stone obelisks, the tallest of which loomed 98 ft over the cemetery in which it stood and weighed 517 tons. Ezana is also known for converting much of Ethiopia to Christianity, around 330 AD. One legend has it that the Ark of the Covenant containing the remnants of the 10 commandments of Moses was brought to Aksum, and Coptic monks have protected it ever since.
Aksum flourished until the 6th century AD, maintaining its trade connections and a high literacy rate, minting its own coins, and building monumental architecture. With the rise of the Persian empire in the 6th century AD, the Arabic world redrew the map of Asia and excluded the realm of Aksum from its trade network, and Aksum fell in importance.
http://archaeology.about.com/cs/africa/a/aksum.htm