I can't even imagine. I toured a C-17 some years ago and THAT amazed me.
A C-17's interior can be configured any number of ways but in the one I explored there were also stairs leading to the cockpit. At the top of the stairs was, wellllll, I can only describe it as a 'balcony'.
I remember thinking if one fell off the balcony to the lower level it would kill you.
Pretty sure I wrote about this before but I was once on my downwind leg for a landing at Fresno Intl. Airport and saw a C-5 taxing down the runway I was cleared to land on... that is, I "thought" it was taxing.... to my shock the nose of the C-5 suddenly rose and not long after the C-5 took off. How could I have thought it was 'taxiing'?
Because those planes are SOOOO huge your perspective is thrown off. The C-5 took a while to travel it's own length down the runway EVEN AT takeoff speed! I was so mesmerized watching the C-5 takeoff I missed my turn to base... but that's another story.