In a great article in USA Today, people on a cruise explore the Panama Canal from the perspective of a Celebrity Cruise line ship that makes the transit.

PANAMA CANAL, Panama — It’s barely an hour after daybreak when the Celebrity Millennium enters Balboa Harbor near Panama City, leaving the Pacific Ocean behind, but already the ship’s outer decks are lined with passengers.

Dead ahead is Miraflores Locks, one of three sets of giant rectangular chambers that will lift the 91,000-ton Millennium up and over the Continental Divide to the Atlantic, and the excitement is palpable.

“This has been on my bucket list for a long time,” says Don Hendon, 70, of Longview, Texas, as the 106-foot-wide Millennium squeezes into the first of the chambers with two feet to spare on either side.

Hendon watches as seven-story-high steel gates slowly swing shut and the basin begins filling with millions of gallons of water. At 1,050 feet long, the lock is roughly the size of three football fields.

“It’s massive, isn’t it?” he says.

Massive, indeed. A century after its construction by the United States, the 48-mile-long Panama Canal remains a marvel of modern engineering — and one of cruising’s great destinations.

In addition to the Millennium, more than a dozen other cruise ships regularly voyage through the waterway, which is drawing renewed attention from vacationers as it prepares to celebrate its 100th anniversary next summer. More soon could be on the way as an expansion of the canal scheduled for completion in 2015 allows for wider and longer vessels.

For cruisers such as Jill Schwaertzl, 70, of Vancouver, B.C., a classic Panama Canal cruise such as this one — a two-week voyage that begins in San Diego and ends in Fort Lauderdale — offers a chance to see a man-made wonder that some have likened to the Great Pyramids of Egypt. Far more complex than the Suez Canal that connects Europe to Asia, the Panama Canal cleverly harnesses the dammed water of Panama’s rainforest — and gravity — to power its lock system.

“I’m just amazed at it all,” says the retired banker, gazing from the pool deck as the Millennium approaches the Gaillard Cut, a miles-long section of the canal blasted out of a solid mountain. “It’s fascinating the way they got the water levels to work this way.”

An engineering wonder

As passengers learn during lectures and documentary showings in the days leading up to the Millennium’s arrival at the canal, as many as 50,000 workers at a time toiled for a decade to carve the passageway out of the dense Panamanian jungle. In addition to building giant locks near both oceans, the project required the construction of what at the time was the world’s largest dam along the Chagres River and the creation of one of the world’s largest man-made lakes.

The work was brutal, and more than 5,000 workers died from accidents and illness from 1904 to 1914; an earlier attempt by the French in the 1880s had left 22,000 dead.

Still, the result would change the world. In addition to cruise ships, thousands of container ships a year traveling between the Pacific and the Atlantic oceans use the canal to shave 8,000 miles from a journey that otherwise would involve a two-week sailing around South America. Even after a century, it’s still big enough to handle all but 8% of the world’s shipping fleet.

The Millennium spends an entire day crossing the waterway from the Pacific to the Atlantic. As a Panamanian guide narrates from the bridge, passengers watch, transfixed, as the ship is raised 85 feet above sea level by a succession of two sets of locks before passing through the Gaillard Cut to 21-mile-long Gatun Lake. From there, it returns to sea level via the three-step Gatun Locks before emerging in the Atlantic.

The entire process takes just nine hours.

‘Mind-boggling’ vistas

As is the case with many Panama Canal cruises, Millennium passengers get a second chance to experience the canal the day after the transit when the ship docks in Colon, Panama, not far from the canal’s Atlantic entrance.

A shore excursion takes them to Gatun Locks, where they watch from a platform as container vessels pass through the same chambers that the Millennium navigated the day before.

The four-hour outing includes a stop at a new set of locks under construction that are part of the expansion of the canal.

“Mind-boggling” is how Millennium passenger Barbara Sarjeant, 78, of New Plymouth, New Zealand, describes the building frenzy on view from the visitors center. Stretching out over more than a mile, the new locks are well underway, with giant concrete walls already in place and hundreds of workers scrambling over six-story-high structures that will hold some of the largest gates in the world.

“Those workers look like little ants down there,” Sarjeant notes.

Begun in 2007, the expansion could be a boon for the cruise industry. Though the canal is large enough now for most of the world’s cruise ships, lines such as Royal Caribbean and Carnival in recent years have been building vessels even bigger than the maximum size allowed in the locks. At 180 feet wide and 1,400 feet long, the new lock chambers will allow such iconic ships as Cunard’s Queen Mary 2 to transit the canal for the first time.

Most of the major lines offer canal cruises. Many, such as Royal Caribbean and Carnival, operate just a handful of the sailings each year as they reposition vessels between winter homes in the Caribbean and summer homes in Alaska. Others, such as Princess, offer regular trips from late September through April.

In general, the voyages are long and leisurely, with lots of sea days. As with this 15-night Millennium sailing, the typical “full transit” is a one-way trip from California to Florida, or vice versa. Some lines also offer a partial transit — a shorter, round-trip voyage to the canal from Florida that includes a passage through the Gatun Locks only as far as Gatun Lake. Either way, it never fails to impress.

“I’ve had friends go through it and say it was spectacular, and they were right,” says Joanne George, 70, of suburban Philadelphia. “It’s more than I expected.”

More pictures here

If you go

Celebrity Cruises offers 15-night Panama Canal voyages from San Diego to Fort Lauderdale, or vice versa, on several ships each year between September and April. Fares start at $1,329 per person, based on double occupancy, for a windowless “inside” cabin. Information: 800-647-2251; celebritycruises.com.

Also offering regular Panama Canal sailings is Princess Cruises. The line’s Island Princess and Coral Princess operate 10- and 11-night “partial transits” of the canal round-trip from Fort Lauderdale, as well as longer 15-night “full transits” between Fort Lauderdale and Los Angeles, between October and May. Fares start at $899 per person for the shorter trips. Information: 800-774-6237; princess.com

Other major lines with Panama Canal cruises include Holland America, Royal Caribbean, Carnival, Norwegian, Disney, Windstar, Oceania and Crystal.