John Gill Commentary Daniel 4:10

"Thus were the visions of my head upon my bed: I saw, and, behold, a tree in the midst of the earth; and the height thereof was great." — Daniel 4:10 (ASV)

Thus were the visions of mine head in my bed So things appeared to my fancy thus; they ran in my head or brain in a dream in my bed, as if I saw them with my eyes, as follows;

for so I thought, I saw, and behold a tree in the midst of the earth; an emblem of a powerful prince well settled, and strongly supported in his power and government; so the Assyrian monarch, (Ezekiel 31:3–9) and here Nebuchadnezzar himself, as it is afterwards explained; who was well established in his monarchy, the metropolis of which was Babylon; and which stood pretty much in the midst of the then known world:

and the height thereof was great; taller than trees in common; denoting the superiority of the Babylonian monarch over all kings and kingdoms of the earth.