What architectural achievement of Nebuchadnezzar II is considered one of the Seven Wonders of the Ancient World?

The Hanging Gardens of Babylon are traditionally counted among the Seven Wonders of the Ancient World and are associated with Nebuchadnezzar II. The Ishtar Gate and Walls of Babylon were also important Babylonian structures, but they are not the Wonder named in the question.

AI-written and checked against the verified answer.