It's easy to see how a natural sight like the Great Barrier Reef is an educational adventure, but few man-made structures rise to that level -- unless they have a system of locks, like the Panama Canal. Started in 1880 and completed in 1914, the Panama Canal was named one of the seven wonders of the modern world by the American Society of Civil Engineers (ASCE). According to ASCE, the workers who built the canal moved enough dirt to open a 16-foot wide tunnel to the center of the Earth.
The canal stretches from the Atlantic (via the Caribbean Sea) to the Pacific and drastically shortened the time it took to move cargo between the two oceans (ships used to have to sail down below the tip of South America). It also opened up the interior of Panama. In addition to featuring some of the most impressive modern engineering in the world, the Canal cuts through verdant rain forests. It's also an historic achievement, one that required massive amounts of international cooperation and coordination. While most educational adventures reward people who love science, the Panama Canal is a great adventure trip for history buffs as well.
You need a boat to traverse the Panama Canal (duh). Large cruise ships offer routes that cover the canal; these routes are a way for the cruise companies to make money as they move their ships from the Atlantic to the Pacific for different sailing routes and seasons. You can also go on a smaller, more tour-oriented cruise or charter your own boat and take it through the canal yourself. That final option assumes you know what you're doing. Boats that are less than 50 feet (15.2 meters) in length pay a toll of $1,300 to use the canal.