OTTAWA - It doesn't have quite the cachet of the Great Pyramids of Giza, India's Taj Mahal or the sprawling palaces of ancient China, but the United Nations has declared the "monumental" Rideau Canal a world heritage site.

The canal's practical uses as a commercial and strategic alternative to the St. Lawrence River have long since been overtaken by highways, railways and flyways, gigantic transport ships, mile-long trains and cursed tractor-trailer trucks.

It is probably best known now as a tourist magnet and home to "the world's longest skating rink," but the canal was lauded by the United Nations Educational, Scientific and Cultural Organization (UNESCO) because "it bears witness to the fight for control of the north of the American Continent."

Meandering its way 202 kilometres from Kingston, Ont., to Ottawa, this wonder of early 19th-century construction hits such high points and hot spots as Beveridges, Poonamalie and Kilmarnock.

Summer staff still open and close its 50 locks by hand, but now they do it for those living lives of leisure aboard cabin cruisers and oversized yachts.

"I think (the designation) is going to have a positive impact," lockmaster David Dicaire said Thursday. "I think it's good for marketing.

"Perhaps we'll get some more money or grants to fix the infrastructure, which is in dire need. It's 175 years old. It would be nice to be able to fix it up."

The canal is the 14th Canadian locale to be declared a world heritage site, joining the likes of Alberta's 75-million-year-old Dinosaur Provincial Park, the 11th-century Viking settlement at L'Anse aux Meadows on Newfoundland's Great Northern Peninsula, and the 18th-century shipbuilding capital of Lunenburg, N.S.

Connecting the Rideau and Cataraqui rivers since it opened in 1832, it was one of the first canals to be designed specifically for steam-powered vessels. But its heyday was short-lived, and most commercial traffic reverted to the newly tamed St. Lawrence in the 1850s. The canal's military, commercial and transportation value expired completely after the First World War.

"All that saved the system from abandonment was the high cost of taking it apart," says a Parks Canada history of the Rideau.

That would have been an ignoble end to what had been a grand endeavour -- and one that came at great cost. Its financial price was a paltry 800,000 pounds, but 400 men died in its construction, mainly from mosquito-borne malaria.

To build the canal, Lt.-Col. John By, its principal designer, had two options before he began the six-year construction project in 1826.

The conventional and proven option was to use excavated channels of considerable length to link existing waterways that were navigable, bypassing falls, rapids, swamps and rocky shallows.

By dismissed this approach as being too expensive and time-consuming, given the terrain, geology and configuration of the lakes and rivers.

Through what Parks Canada described as "a fundamental stroke of creative genius," he envisioned another option to join the watersheds of the two river systems.

The relatively untried technology was called "slackwater." It would use a large number of embankments and high dams to inundate shallows, swamps, and rapids, thus creating a series of impoundments deep enough to navigate the full length of the canal.

This approach dramatically reduced the requirement for extensive excavated channels, reducing costs and construction time.

Slackwater techniques had been attempted in North America, but none of these canals was near the complexity of what By conceived to join the Rideau and Cataraqui rivers.

The Corps of Royal Engineers responded with designs for an ingenious system of engineering works to exercise unprecedented control over water levels. They included 74 dams and 47 locks at 24 lock stations, allowing vessels to ascend 85 metres to the summit of the canal from the Ottawa River, and then descend 50 metres to Lake Ontario.

Part of By's genius was his foresight in planning for the future dominance of steamboats. The specifications for the canal that he was given called for locks sufficient in size to accommodate Durham boats, flat-bottomed vessels propelled by sail or oars.

Soon after his arrival in Canada, By sought, and was given, authorization to build locks able to accommodate vessels using the newly emerging technology of steam power.

The system was also peppered with fortifications -- six blockhouses and a fort, initially. Defensible lockmasters' houses were later added at several lock stations and, between 1846 and 1848, four Martello towers were constructed to strengthen the fortifications at Kingston harbour.

"It is the best preserved example of a slackwater canal in North America demonstrating the use of this European technology in North America on a large scale," UNESCO said in its letter of designation.

"It is the only canal dating from the great North American canal-building era of the early 19th century to remain operational along its original line with most of its original structures intact."