NAZARÉ, Portugal -- The big ones typically come only once a year, in the winter. Whipped up by powerful storms in the North Atlantic, they roll for days toward Europe, rising to seemingly impossible heights before crashing on the shores of Praia do Norte, a beach along the Portuguese coast just north of this picturesque fishing town.
"It is like an earthquake," said Pedro Pisco, a city hall administrator from this old fishing port, a few miles away from Praia do Norte. "When it breaks, you can feel the earth shaking under your feet."
The area has a reputation as a dangerous spot for its turbulent gales, crushing surf and frequent accidents, though on a recent day the sea was flat as a reflecting pool. Normally, though, the waves crash on shore with a special power, and for years residents were not even sure they were safe to surf.
Despite its charm and a stunning 14th-century church, Nazaré has seen some bad times, with the decline of its once-prosperous fishing industry and an exodus of local youth. And that was before the euro crisis and the deep slump in the Portuguese economy.
But thanks to a photo that electrified the world last month -- showing a big-wave surfer named Garrett McNamara setting what is expected to be a world record, streaking down the face of an estimated 100-foot breaker -- the city is now busily trying to cash in on its moment of fame to promote itself and its now famous beach, Praia do Norte, as a pre-eminent big wave surfing spot.
The waves here have long been compared to invincible enemies, killing fishermen, vacationers and frequently inundating streets and shops. There is even a spot called "the reef of widows," where by legend the wives of fishermen would watch their husbands drowning after waves had destroyed their boats.
The town is still filled with widows wearing black dresses or the traditional seven layers of multicolored petticoats and long socks. A local legend says that women wore seven skirts because while waiting for their husbands to sail home, they would count seven waves until the sea would calm down.
Dino Casimiro, a 35-year-old body-boarder from Nazaré, is an ardent admirer of the waves and one of the major initiators of the city's image makeover.
"For many years, we didn't know if the waves were surfable or not," said Mr. Casimiro, a physical education teacher in several local schools. "They were too big."
In 2010, with the town's big-wave fame spreading, several of the biggest names in surfing -- including Mr. McNamara, who lives in Hawaii, and Kelly Slater, Shane Dorian and Tiago Pires, the Portuguese surf champion -- came to Praia do Norte. "Praia do Norte is the best secret in the world," Mr. McNamara said by telephone from Hawaii. "There is nowhere in the world where you can be so close to the giant waves."
The project, called the "Zon North Canyon show" and developed with Mr. McNamara, was aimed at promoting him as well as the town. It was sponsored by Zon, Portugal's main media holding company, after Mr. McNamara broke his first world record here by surfing a 78-foot wave.
Then last month Mr. McNamara spent about 30 seconds on the face of a giant wave still spoken of with awe by other surfers. "It was like riding a mountain, like snowboarding down a giant mountain," he said.
There are big wave spots far from land, like Cortes Bank 100 miles west of San Diego, Calif. But there are very few in coastal areas, because the gently sloping continental shelf normally flattens out the giants, gradually sapping their strength before they can reach land. But this small part of the Portuguese coast sits at the end of a giant funnel called the "canyon of Nazaré," 130 miles long and 16,000 feet deep (at its deepest), that points like an arrow toward the town.
The canyon, said Luis Quaresma, an oceanographer at the Lisbon-based Instituto Hidrografico, creates "a highway for the swell," which arrives with a lot of energy, very close to the beach. "While the waves here are almost always imposing, local people say, occasionally -- on average, once a year -- a few swells of almost unimaginable height will roll in," he said.
As a child, Mr. Casimiro says he would look at the waves almost every day from the 16th-century fortress and its lighthouse set atop a cliff overlooking Praia do Norte. "Just looking at the waves scares you," he said. "They are very strong, powerful and hollow."
In 2005, he bought a camera, took pictures of the most impressive waves at Praia do Norte and sent one to Mr. McNamara, who he knew only from the Internet.
"Garrett called me at 3 a.m. once," Mr. Casimiro said. "He had seen the forecast."
The swells are picked up by a midocean buoy several days before they come ashore, enabling big-wave surfers like Mr. McNamara to scramble to Nazaré in time to catch them. In recent years, Mr. McNamara has caught high waves in places like Tahiti, Hawaii and even on the coast of south-central Alaska, where he surfed tsunami waves formed by calving glaciers.
But Nazaré, he said, holds a special place in his heart. "It's a place for everybody to go enjoy, it doesn't matter if you surf or not," he said.
Here, in a town that welcomed Vasco da Gama before and after his trip to India more than 500 years ago, Mr. McNamara is considered a modern hero of the sea.
Some days, when he surfs Praia do Norte, the children of the local school interrupt classes to watch him streaking down the breathtakingly high mountains of dark water.
In April, Mr. McNamara and the city will inaugurate a "High Performance Center" to teach people the dangers of the sea and to promote surfing and environmental protection.
Mr. Pisco, the city administrator, also plans to turn the fortress and its adjoining lighthouse into a museum of the big wave with a panoramic viewpoint.
From this particular spot, Mr. Pisco said, "you see the giant wave forming off in the distance and then growing little by little," he said. "In a matter of a few minutes, it breaks like an explosion."
Correction: February 25, 2013, Monday
This article has been revised to reflect the following correction: A previous version of this article misspelled the name of surfer Garrett McNamara. It is Garrett, not Garett.
This article originally appeared in The New York Times.