The heart of the Panama Canal is its great watery center, Gatún Lake. This immense, island-studded reservoir formed when the canal was built in the early 20th century. From the lido deck of my cruise ship, the Crystal Symphony, the islands' shorelines looked strangely irregular, and at first I couldn't figure out exactly why. As the ship neared one, though, the reason became clear: There is nothing resembling a beach anywhere; the verdant tropical jungle simply explodes out of the lake at the waterline.

Just a hundred years ago these islands were mountaintops, and when central Panama's rivers were dammed to form Gatún Lake, the rest of the mountains were submerged. Richard Morgan, a retired Canal Zone executive and an expert on the canal's history and technology, was my guide through the Panama Canal. He said that as the water quickly rose, bewildered onlookers on ships observed the green trees of the dry mountaintops growing blacker and blacker. "On closer inspection," Morgan said, "they found that the limbs were covered with tarantulas, clustering together in huge clumps, desperately climbing up from the jungle."

As an engineer, I have great appreciation for the world's modern technological marvels. I've made pilgrimages to see the best of what my fellow thing-makers can do: the Giza Pyramids, Hoover Dam, the Eiffel Tower, the Channel Tunnel, to name a few. But in terms of far-reaching impact on the world, perhaps no other human construction compares to the Panama Canal. So when I had an opportunity to take a technology-themed cruise from Miami to Los Angeles, I jumped. The highlight of the trip was right in the middle: a transit of the storied canal, a place of great import, historically, scientifically and politically.

Arachnids aside, no other freshwater lake sees the frenetic variety of activity that Gatún Lake hosts. As the cruise ship, accompanied by two large tugboats, made a 5-knot run southward to the Pacific, we shared the lake with oil tankers hauling jet fuel, Liberian-flagged grain freighters and legions of container ships, some bearing upwards of 4,000 20-foot-long steel containers. In addition to these transient visitors, there were resident suction and dipper dredges, navigation maintenance launches, patrol boats and the odd pleasure yacht. Morgan said the freighters pay the canal agency more than $100,000 each to make the transit, which seems expensive until he explains that the fee charged to the cruise ship line for this single passage was about $200,000.

While that is a lot of money by any conventional measure, for the Panamanians the canal is not a golden goose. This is one huge and immensely expensive operation, and most money collected in tolls is plowed back into canal operations. There are tugboats to pay for, dredges to operate, lock doors to overhaul, concrete to maintain. Of the $20 billion in tolls collected annually, the country of Panama sees only about $100 million, according to Morgan.

Gigantic construction project

Operating the canal profitably is a tricky business proposition. If the price is too high, ship owners might choose another route or even unload their containers at U.S. ports and send them by rail across the continent. Plus, the largest freighters and cruise ships are too large to fit through the 1910 vintage locks.

To fix that, the outfit that runs the canal, the Panama Canal Authority, is mightily expanding the waterway. As we passed through the southernmost set of locks at Miraflores, a gander to the starboard side showed one of the world's largest construction projects in full swing. As far as the eye could see were trucks and cranes, bulldozers and road graders. To the unaided eye, it looked like a termite colony. Gazing through binoculars, I could appreciate the project's enormity. Millions of tons of earth and rock had been broken, loaded, transported and dumped. Towering concrete walls were poured, set and cured. A human-built river flowed where a large hill had towered just a few years earlier.

The project is planned for completion on Aug. 15, 2014. It's a sweet, semi-poetic bit of technological project planning. That is the 100th anniversary of the original canal's opening, when the steamship Ancon made the inaugural passage.

When the new locks and canal are ready in 2014, shipping experts say, cargo capacity will double. The huge 13,000-container ships and the latest generation of wide-body cruise ships -- called "post-Panamax" because they exceed the current canal's maximum width -- will glide through a still relatively tiny crack in the 10,000-mile-long continent's continuity.

Guided through the locks

Our ship, sailing from the Caribbean, entered the canal from the north. (Somewhat counterintuitively, the direction of travel from Atlantic to the Pacific is north-south, not east-west, because the Panamanian isthmus jogs out in an inverted "S" shape along the 9th parallel.) We passed the Atlantic port cities of Cristobal and Colon and steamed into the wide main channel. I noticed a narrow passage off to starboard, with a shoreline too regular to be natural. Morgan explained that it was a remnant of the tragically unsuccessful French effort to build a canal back in the 1870s.

In a driving rain, we came to the first set of locks, called the Gatún Locks. As we approached, a small rowboat came alongside to deliver a set of lines that the ship's deck crew pulled aboard and fastened to capstans inside the ship. The land-side ends of the cables were attached to six small electric railroad engines, known as "mules." These small but muscular mules guide the ships through the locks.

Once we were inside the locks, the great gates swung closed, and water from Gatún Lake bubbled into the concrete chamber through underground tunnels. Our ship, all 51,000 tons of her, rose about 85 feet through three interconnected locks.

At the far end of the Gatún Locks is Gatún Lake. The first mile or two of shoreline to port is an unnaturally flat-topped, grass covered hill. This is the dam that formed the lake. When it was built in the early 20th century, it was the world's largest dam. Because it lay in the middle of a rainforest, with 130 rainfall recharges a year, Gatún Lake has more than enough water to operate the locks with no need for pumps. But we lucked out: Shortly after we cleared Gatún Locks, the rain was replaced by intense tropical sunshine.

As a passenger ship, the Symphony flew a special flag from its signal mast -- the letter "Z" in nautical flag code -- that gave it priority over freighters. We breezed by other ships moving through the lush and environmentally protected 20-mile-long lake.

At the lake's southern end is the famous Gaillard Cut. More than 9 miles long, it was the route U.S. engineers selected through the continental divide. Excavating Gaillard Cut was the canal project's most difficult task. At peak, 60 steam shovels and 150 trains were in constant motion, removing the ground for the 300-foot-wide, 40-foot-deep channel.

From the southern end of the cut, our ship passed through the two remaining sets of locks, called Pedro Miguel and Miraflores, respectively. Just beyond them lay the administration buildings of the Canal Zone, looking hot but shipshape in the bright sun.

As we cruised on, gleaming white skyscrapers of Panama City came into view. The city is far larger and more modern-looking than I imagined it would be. A line of skyscrapers stretches for miles, all of them white, some quite striking in architectural profile.

Finally, eight hours after departing the Atlantic, we reached the Pacific. Leaving the channel, the ship's stacks just passed beneath a pair of bridges, and we headed out into the Bay of Panama, where innumerable ships lay anchored, quietly waiting for their turn to enter the canal.

Through the narrow ditch that is the Panama Canal flows 5 percent of the world's goods. That cargo volume is predicted to double when the new canal is completed.

The 20th century saw dozens of huge civil engineering achievements. But to me, the Panama Canal stands alone as a triumph of engineering, a project that improves the quality of life for nearly everyone on Earth.

Minneapolis-based William Gurstelle is an editor at Popular Mechanics magazine and author of best-selling DIY science books "Backyard Ballistics" and "The Practical Pyromaniac." Visit him at