In Norse Mythology, there's a rainbow bridge between the land of the gods and the land of men. It's called Bifrost, and a few other names as well.
In Schiller and Rand, art is seen as such a bridge, between the the human power of abstraction and the human power of perception, between the human sense of the moral ideal and the human recognition of the difficulties of living morally.
Schiller describes the problem to be bridged as a gulf or opposition. Rand sees it as ultimately a computational challenge, which art is capable of solving, by means of subconscious integration.
I'm sure that somehow this issue can be chased back to Plato.
The rainbow bridge takes you up into the blue.
Forgetting your fear of heights,
charge forward and push till the journey is through,
absorbing the pulsating lights.