From the IcefieldsParkway - Canada's most scenic driving route - their monumental work is displayed in ever-larger peaks, rising like ruined castles on either side of the road.
As we venture down the extraordinary IcefieldsParkway in vans with our super-active, super-attentive guides, Dani Houston, Felicia Perricelli and Andrea McLeod, (pluck is their natural personality) the huge cascading walls of rock we pass look to have the remains of ancient mountain top cities.