A magnificent engineering and managerial achievement which speaks volumes about the US vision of itself in the early 20th century. Also a major contributor to the developent of world trading patterns etc
If not the wohle "canal" then at least a set of locks and perhaps some of the company housing and the Admin block in Panama City which, I seem to remember contains a wonderful Mural "of its time"! Plus perhaps The Gailard Cut.
Back really with Fallingmeltwater's comments re the Dresden bridge about whether UNESCO should insist that its sites don't undergo any development - I guess a site like the Canal which cannot be "preserved" in the way which UNESCO seems to expect its sites to be preserved would never get accepted - yet it is the Gothic cathedral of its age which set new boundaries and rewrote the way the world operated.