Here is the number that genuinely breaks perspective.
Olympus Mons is so wide — and its slope so gentle — that if you were standing at its base...
...and you looked toward the summit...
...it curves below the horizon of the planet before you can see the top.
That's not a metaphor.
The mountain is so large that the curvature of Mars itself hides the peak.
The slope rises at less than three degrees.
You would walk for hundreds of kilometers across the volcano's surface...
...and you would be stand