the night sky is three-dimensional
The first time I truly understood this was on a summer road trip to the Oregon coast. Most of the journey south from Portland, after leaving I-5, takes you far from any significant human settlement. The forest still rules here, despite the occasional scar from a clearcutting operation.
Late at night, cresting over a ridge on Highway 42, I almost lost control of our faithful Firenza wagon as THE ENTIRE UNIVERSE came staggeringly into view. I had noticed the stars earlier, in brief glances between corkscrew turns, but now we were coasting down into a steep valley, and the horizon seemed to have dropped down 30 or 40 degrees to provide my father and I with our own private OMNIMAX theatre of the heavens.
All the spaces in between the bright stars were filled with other stars, and the Milky Way was plain as a road striping accident. But the most incredible part was the sense of immense distance as I realized I was looking at the very depths of space - not to mention time traveling millions of years to when the light was emitted from those distant galaxies...
This constitutes one of my only gripes with city life: the inability to experience this wonder to its fullest extent.