Panama Canal
It was decided that the canal would have locks at both ends and Lake Gatun in the middle would be some 50 feet above the oceans on either side - Atlantic and Pacific. The work took 10 years and to my wonderment the original locks and their gates are still the original ones. From ocean to ocean it is about 45 miles.
There are three locks on either side to raise up the ships from the Pacific side and then lower them at the Atlantic side. An incredible feat of engineering.
By using the canal ships can save 2,300 miles by not having to round Cape Horn. As ships have grown larger a new set of lock gates either end were constructed and now are able to accommodate super tankers - in fact super tankers are now built to fit into the new locks. The tariff for the largest container ship can be as high as $1 million!
I knew that I would enjoy the day sailing slowly into the three locks and then across the lake to the other side but I simply was in awe of the accomplishment. It will remain as a day to remember and I would highly recommend taking a cruise to see how the system works.