Originally Posted by Zeke

Even small lakes follow the curvature of the earth. Thinking theoretically, if one had a level capable of seeing a highway built exactly level, it would rise as a tangent to the curvature of the earth. The earth curves 7.68" per mile. So a dead level highway a 1000 miles long would be 768 feet high at the far end.

Dead level Los Angeles to Las Vegas and you could just about step out of your car at the penthouse of the MGM Grand. (not quite — 230 feet vs. the total height of the MGM at 293.)