Well, it doesn't.
Obvious though the rest of this post might seem, there really is, no matter what preparation you've done, something absolutely incredible and unmatched about standing next to - or in - something truly ancient, or something that has otherwise greatly impacted history. When something you've seen hundreds of times in photographs is suddenly RIGHT THERE IN FRONT OF YOU.
Something amazing about actually touching it, or walking through it, rather than just looking at it in a photograph.
Something almost religious about being able to walk around it, or look at it from both sides, or appreciate its actual scale in a way you never could a mere picture.
Something humbling about realising that ancient people have stood in that very spot and left no trace, and that future generations will do likewise and there will be no trace of you.
Something chilling about imagining what events would have been occurring decades, or centuries, or millenia ago in the very spot on which you're standing. And that anyone looking at a photograph of you in that spot would immediately know exactly where on the planet you were.
It is, in fact, awesome.
PS I'm sorry, Colosseo, for taking liberties touching up your columns.