Fact
Olympus Mons is roughly the size of France
Stand on it and the slope is so gentle you might not know you were on a mountain.
The Martian volcano rises about 22 kilometres – two and a half times Everest – and spans some 600 kilometres. Its shield shape means average slopes are only about five degrees, so a climber would experience a long gradual rise, with the summit beyond the horizon for most of the ascent.