I know this may piss you off, but I must give you my honest opinion. Mr. Levi obviously has an appreciation for stone architecture, but lacks the technical knowledge regarding how such structures were/are built. He is like a native who has lived his entire life on an island, only to be faced one night by a shipwrecked individual operating flashlight. Because he lacks the knowledge to understand what it is he is seeing, he defers to his imagination.
Mr. Levi categorizes certain aspects on the creation of Mt. Rushmore as "anomalous". He looks at a two dimensional image of an incomplete Mt. Rushmore, and infers that there is no way they could have carved another head, as (per the image) there is not enough stone to achieve the task. He reminds me of those who (due to a lack of technical knowledge) cannot fathom the achievement of landing a man on the moon, so they claim that it was an elaborate Hollywood produced hoax.
Are Mr. Levi's inferences deliberate, I wonder? What may or may not be known to him, his trivialization of human achievements is textbook Marxian mind-fuckery.