When one thiks of engineering marvels and achievements, the Panama Canal has to jump right in to your thoughts. When the decision was made to link the Atlantic and Pacific Oceans, it was determined that the place to do this was through the country of Panama. In hindsight, could they have thought of a more difficult place to do this?
The number of men who gave their lives to this project, both by accident and disease, measured in the tens of thousands. Most of this number was caused by disease, yellow fever specifically. When the cure was found, the building process went much more quickly.
Instead of just going straight across the country, the decision was made to actually have the canal go through the country on a north/south tangent. An interesting fact is that the Pacific entrance to the canal is actually east of the Atlantic (Caribbean) entrance. (That's a bit of trivia that can be used with your friends.)
The cost of ships crossing the canal, now that it's owned by the country of Panama, has gone higher substantially. The "average" cost for a cruise ship is $250,000. For freighters, tankers, and other commercial transport ships, it is still a lot cheaper than having to go around the southern end of South America.
There are two sets of locks to go through to transit the canal, and the length of the ship cannot exceed 1,000 feet. Therefore, many ships that are built are kept at or below this length.
A complete transit through the canal "normally" takes 8 hours, and when you consider the large number of ships that "go through" daily, it is a remarkable achievement.
There are observation buildings at each of the locks (Gatun and Miraflores), and I would strongly suggest that you plan on spending some time at either of them and really get to understand and appreciate this wonder.