The heart of the kingdom was a large city, covering at least 60 acres, which flourished 300 miles south of ancient Egypt in what is now Sudan. It was founded long before the civilisations of Ethiopia, northern Nigeria and Zimbabwe, which are respectively 2,600, 2,400 and 1,000 years old.
Archaeologists first found its ruins in and around the modern town of Kerma in the 1920s, but they immediately assumed that it was a distant military outpost of ancient Egypt and remained unaware that an entire city lay beneath the site.
Excavations have unearthed temples, palaces and houses of what is being tentatively identified as the Biblical land of Cush, mentioned in the Book of Genesis in the Hebrew Bible, but misleadingly referred to as Ethiopia in English versions. Noah's grandson was named Cush and some scholars have suggested that the land of Cush took its name from the Biblical character.
After more than 10 years of excavations, archaeologists led by a Swiss professor, Dr Charles Bonnet of Geneva University, are now unearthing the remains of a 200ft- long royal palace in what they believe was the capital of a kingdom almost as big as Egypt itself.
A spectacular temple and the remnants of a 1.5-mile-long city wall, 40ft thick and partially made of fire-baked red bricks, have also been discovered. This is the earliest known systematic use of fired bricks in the world.
It is estimated that the city had a population of between 2,000 and 3,000. Some buildings were thought to be several storeys high, perhaps reaching heights of more than 70ft.
The royal palace, discovered earlier this year, has a 46ft-long throne room with a raised dais at one end. In its nine other rooms, the archaeologists have unearthed dozens of finds including a gold and rock-crystal pendant, most of a 20in-high yellow and red painted male ceramic statue, and hundreds of tiny slabs of clay ready for use as official trading 'stamps'.
The 160ft-long main temple - inside a walled religious complex - was probably dedicated to sun worship. The excavations have now located the central 'holy of holies' linked to a terrace by a 65ft-high stairway.
Professor Bonnet's team has also investigated dozens of tombs - many of them involving human sacrifice. Some individuals were buried with up to a dozen sacrifices, believed to be slaves or family members. The king was buried with more than 400 sacrificed men, women and children.
The Cushite civilisation first began to develop in around 3200BC, grew rapidly after 2400 and reached its peak between 1750 and 1500 BC. At that point it appears to have stretched for 700 miles along the Nile between Aswan in southern Egypt and the Fourth Cataract, 200 miles north of what is now Khartoum.
The peak coincided with a low point in the fortunes of ancient Egypt, which had split into three principalities. The Nile delta had been taken over by settlers from Palestine known as the Hyksos (ancient Egyptian for 'foreign chief').
The kingdom of Cush was finally conquered by Egypt in around 1500BC. Signs of burning from the attack have been found by the archaeologists.