The Hanging Gardens of Babylon were listed by Greek historian Herodotus as one of the Seven Wonders of the Ancient World. At the time he reported two different creation stories that existed at the time. The first is the more popular story that King Nebachadezzar II of Babylonia built it around 600 BC to comfort his homesick wife Amyitis. Others believe that it was created during the reign of Queen Shammuramat of Assyria around 810 BC.
While the creator is up for debate the actual location has also been questioned. Most early references put the garden in Babylon but some speculate that the actual location may have been 350 miles to the north in the city of Ninevah. King Sennacherib of Assyria had gardens built in Ninevah around 700 BC and there may have been some confusion between the two.
Following the most accepted Nebachadezzar version the Hanging Gardens of Babylon were built on along the east bank of the Euphrates River. Babylon was about 80 km or 50 miles southwest of modern Baghdad in Iraq. The gardens grew on many levels of terraces made mostly of mud bricks on an area 122 meters by 122 meters or 400 feet by 400 feet and were 22 to 24 meters or 72 to 80 feet high. The vaulted terraces were one above another as they rested on cube shaped pillars. An irrigation system which utilized the Euphrates watered the extensive garden continuously. The Gardens were believed to have been destroyed by an earthquake in the second century BC and the mud bricks disappeared by erosion.
Ancient Seven Wonders page