There is a bridge in a hollow shape
And a hundred going over it
No blacksmith, nor mason,
nor carpenter built it really.

Tell me something, which has roots as nobody sees, Is taller than trees, Up, up it goes, And yet never grows?

It is as large as a mountain, as small as a pea, endlessly swimming in a waterless ocean.

What is it?

It can run but never walks, It has a mouth but never talks, It has a head but never weeps, Has a bed but never sleeps.

What can you catch but not throw?