11 For in the vision of Nebuchadnezzar, when he saw it, which Daniel made known and showed to Nebuchadnezzar, when he saw the image which stood over against him, the head of the image was of gold, and its breast and arms of silver, and its belly and thighs of brass, and its legs and feet of iron and potter's clay. And Daniel said to Nebuchadnezzar:— You are the head of gold. And why was he called the head of gold? Was it not because the word of Jeremiah was fulfilled in him? For Jeremiah said:— Babylon is a golden cup in the hand of the Lord, that makes all the earth to drink of its wine. And also Babylon was called the head of all the kingdoms, as it is written:— Babylon was the head of the of Nimrod.
Source: Demonstrations (New Advent)