CAIRO -- Every year, Egyptians mark the arrival of spring by flocking to the rare patches of green in this sprawling, crowded megalopolis to celebrate a holiday believed to be passed down from the pharaohs. Sham el-Nessim, the holiday's Arabic name, means literally "smelling the breeze."
That's not always advisable in the case of the holiday's trademark dish: a heavily salted, aged fish called feseekh that even admirers acknowledge smells more like garbage than food.
"It's terrible!" said Muhammad Shaaban, 54, who lounged with his extended family under a tree in a Cairo park during the holiday on Monday.
But he still eats the fish. "It's an Egyptian tradition that's been with us for 7,000 years," he said. "We're used to it."
These are turbulent times for Egypt as its people deal with recurrent street violence, political polarization and increasing economic distress.
Recent news reflects the gloom. The government has so far failed to reach a loan agreement with the International Monetary Fund that could help prop up the economy, and disagreements rage between the Muslim Brotherhood, Egypt's strongest political power, and its opponents over the direction of the country.
A discussion about whether Muslims were permitted to wish their Christian neighbors a happy holiday on the Coptic Christian Easter this past Sunday was taken by some as an indication of how much society has frayed since the revolution that toppled President Hosni Mubarak more than two years ago.
But those worries were largely set aside on Monday as Egyptians of all classes and religions held picnics, took boat rides on the Nile and celebrated a holiday whose roots most believe date back to this land's ancient inhabitants.
They also stood by their fish.
"Feseekh is Egyptian, and the ancients taught us how to make it," said Maher Dahab, a clothing merchant standing in line at a fish shop downtown. "They built the pyramids, and they made feseekh."
Both the holiday and its stinky meal have proved resistant to attack, highlighting the long history that gives Egyptians one of the strongest senses of national identity in the Arab world.
While most Arab countries were created by colonial powers drawing arbitrary lines on maps, Egypt has been Egypt for millenniums. Pride in that inheritance is something most Egyptians share, even when they disagree on much else.
Despite declarations from a few conservative television preachers branding Sham el-Nessim a pagan holiday that Muslims are forbidden to celebrate, the country's most prominent Islamist parties do not oppose it.
"It's an Egyptian tradition that we've all become accustomed to," said Gehad el-Haddad, a senior official with the Muslim Brotherhood, whose political party dominates the Parliament.
Muhammad Emara, a member of the executive council of the ultraconservative Nour Party, said, "We don't get involved in Egyptian traditions."
Nor have government warnings about the dangers of eating old, raw fish dried up demand.
Two days before the holiday, the Egyptian Health Ministry released statistics for food poisoning and deaths from bad feseekh in recent years: 49 poisoned and 9 dead in 2007; 26 poisoned and 4 dead in 2008; and more than a dozen poisoned and 2 dead in both 2009 and 2010. That's better than 1991, when bad fish poisoned 90 people and killed 18.
While the ministry reported no confirmed cases of feseekh poisoning in the last two years, it warned Egyptians not to eat it, deeming it a health risk that can cause "complete paralysis or death."
One of Cairo's most storied feseekh sellers, Abdel-Nabi Shahin, shrugged when asked about the warnings.
"There are cheaters who give us a bad image," he said, adding that the trick is clean preparation. "Some have dirty fingernails or don't wash their hands before they work with the fish."
The job, he said, requires "cleanliness and vigilance."
Mr. Shahin, 58, is the third-generation owner of the family business, which now has two stores that draw customers from far away seeking fish they can trust.
The process has changed little over the years, Mr. Shahin said. He starts with fresh mullet caught in the Mediterranean, which is washed but left intact, guts and all.
It is packed in salt in wood barrels and left to sit for 45 days. After that, it is good to eat for six months, Mr. Shahin said.
A kilogram of Shahin's feseekh (about 2.2 pounds) goes for about $13, nearly twice what it cost last year because of a fish shortage, he said.
He also sells a smoked fish called ringa that is imported fresh from the Netherlands and processed in a Cairo factory. It costs less than half as much, and you can't smell it across the street as you can feseekh.
The greatest threat to his business is not religious zealotry or government warnings but less vigilant fishmongers who seek to profit from his name, Mr. Shahin said.
A fake Shahin shop opened up across the Nile last year, and he has heard of others, too.
Sitting at a desk in his downtown shop recently while two of his sons sold piles of feseekh to a line of customers that stretched into the street, he fielded calls from people making sure his was the right shop.
"There is only one Shahin!" he shouted into the phone. "All the others are fakes!"
Customers waiting in line disputed the idea that feseekh stinks, or at least tried to.
"It's psychological," said Muhammad Abdullah, 26. "If you smell this smell from a pile of garbage in the street you get grossed out. But if you smell it from feseekh, you don't."
Historians say Sham el-Nessim's genesis remains unclear.
Fayza Haikal, professor of Egyptology at the American University in Cairo, said the holiday could be linked to the ancient Egyptian Festival of the Valley, which was celebrated around April and sought to revive the ancestors. This resembles the modern holiday's focus on the revival of nature after winter, and could explain its association with the Coptic Easter and the resurrection.
Even the celebrations appear similar.
"They shared a meal, they had banquets, they went out, they took boats on the river; it was in some ways very close to what you see now," Dr. Haikal said. "This is why it may relate. But I underline 'may.' "
The holiday has long been observed on the Monday after Coptic Easter, a merger that most likely happened during the early centuries A.D. when many ancient Egyptian practices existed alongside Christianity.
The arrival of Islam in Egypt in 640 apparently did not affect the holiday.
Dr. Haikal said Sham el-Nessim is now a national holiday, not a religious one, and she doubted anyone could strike it from the calendar.
"Festivals are here to cheer people up, and they need something to cheer them up," she said. "They will not give up their holidays easily."
Nor will many give up their feseekh.
On Monday, large families with bags of food staked out patches of grass in the shade of scattered trees at a hilltop Cairo park named after the nearby Al-Azhar mosque and university, Egypt's historic seat of Muslim scholarship.
Some said the government's warnings and recent reports of the police confiscating bad feseekh had made them opt out. But many still indulged, the smell of their meals wafting over the footpaths.
Seated on a blanket in the shade with his wife and three daughters, Mohammed Hassan lifted a yellow-gray fish from a plate, tore it open and drizzled lime juice over its pink flesh.
He said he had heard the warnings, but only bought feseekh from people he knew and trusted.
"It's excellent," Mr. Hassan said, tearing bits of meat from the fish's spine and popping them in his mouth. "There's nothing to be afraid of."
This article originally appeared in The New York Times.