On our way into Cairo, we caught site of the Great Pyramid of Giza! The shear size of this thing is astounding.

What two need to be corrected?

"site" should be "sight"

"shear" should be "sheer"

Explanation:

The two mistakes are "site" and "shear".

"Site" is the location of something; in this case, that's not what the context is trying to say. Instead, the sentence is saying that "we" saw the pyramid, so it should be "we caught sight of the Great Pyramid of Giza".

"Shear" is cutting off the hair of something. Obviously, no one's hair is getting cut, so it doesn't make sense here. Instead, the correct word should be "sheer", which means something like "utter" or to express the power of an item.