Currently in circulation the highest dollar bill is with a face value of $100, although the largest denomination of currency ever printed was the $100,000 Series 1934 Gold Certificate featuring the portrait of President Wilson, but never released for public circulation, only for official transactions between Federal Reserve Banks.
Good, now you're ready for the eastern walls of Olympus Mons. 17Â°23'26.69 N 128Â°57'25.39. W looks challenging enough for you, you can start at 793m elevation and finish at 5642m elevation.
Thus, they are probably not eruption vents. Rather, they are probably collapse pits that formed in the roof of a deeper magma chamber. The size of these pits suggests that the magma chambers in Olympus Mons were fairly large. Likely diameters range from about 20 km to over 60 km. For comparison, calder as in the Hawaiian Islands range in diameter from ~3-5 km up to ~18 km.