Stars. Glowing orbs in the sky, contorting into shapes that don't really resemble anything but our imaginations. And doing this with absolute and total beauty. The milky way racing across the sky as though being dragged by the great horses of Apollo, crashing into the terran absolute on both sides into the great invisible that is the other side. Galaxies, distant and hazy and almost impossible make out with the naked eye - worlds to discover and explore.
I love the night sky. Everything that it contains. The darkness - the brightness - the darkness. Orion's belt (in winter) and the wings of Cygnus (in summer).
It makes you feel small. And young. And child-like. So much to see and explore and see again because you aren't sure you've seen it before. And just as it all starts to make sense you get the sensation that you may be on a large ship in the middle of the ocean, star chart in hand, baffled - trying to make it line up to figure out where on this god-forsaken planet you are. And where you need to be.
It is as though the stars contain all the wonders and dangers of life while also being the metaphor for it.