Vis­i­tors can’t help but be impressed by the sheer scale and mas­sive phys­i­cal effort of the team behind Mount Rush­more Nation­al Memo­r­i­al in South Dako­ta. Look­ing like they’re either emerg­ing from or being absorbed by the moun­tain, the stony faces of past pres­i­dents George Wash­ing­ton, Thomas Jef­fer­son, Abra­ham Lin­coln and Theodore Roo­sevelt – carved 60ft tall in the gran­ite of a Black Hills out­crop – are one of the most famous images in the US.