Ayatollah Ali Khamenei, Iran’s slain supreme leader, had seemed immovable for decades, a man whose authority had become so deeply woven into Iran’s political and religious life that imagining the country without him felt almost impossible.

Now Tehran — the capital from which he ruled, where he was killed and which had shaped his life — is the center of his final journey, filled with mourners for funeral ceremonies taking place across several days, which are part farewell, part spectacle and part turning point.

In the days leading up to the first public mourning, the city changed. First gradually, and then all at once, in the way cities often change before moments of consequence.

Families from provincial towns rolled into Tehran, joining masses who revered Ayatollah Khamenei as patriarch and guardian of the Islamic republic, an order that so many others had long opposed while suffering under its deep repression. Foreign officials, many from authoritarian nations, militia members and religious leaders flew from all over the world, reflecting both Iran’s global reach and its distance from the West.

We traveled there as well, the first visit by New York Times journalists to the country since before the United States and Israel attacked Iran in late February and the government cracked down brutally on protests that started in December. We found a country trying to project strength and stability but pervaded by uncertainty.

We arrived in Tehran, a dense city of around nine million that spreads outward in a sprawl of apartment blocks, glass towers and tree-lined boulevards, with neighborhoods that shift in character from one district to the next. Beside the pomp and circumstance, war-damaged buildings stood scarred along major roads and daily life was still shaped by water shortages and electricity blackouts. Families who lost loved ones in the crackdown were still living with grief — and hoping for justice.

As more people arrived, Ayatollah Khamenei’s presence seemed to expand with them. Across major highways and narrow alleys, in small cafes and sprawling bookstores, portraits of him began to cover the city.

Some show him young, with a dark beard and a stern expression. Others portray the older man many Iranians had grown used to seeing over decades, his beard turned white with age. In some, Ayatollah Khamenei appears beside Mojtaba, his son and successor, the pairing feeling less like a portrait than the passing of one chapter into the next.

The funeral preparations unfolded with the choreography of a major state event. Security checkpoints, organized transportation, public announcements, carefully arranged ceremonial spaces.

We were granted restricted access to the funeral ceremonies by the Iranian government, which closely controlled our movements, and which required a translator and guide to accompany us. It was a quiet reminder of how closely the story itself was being choreographed, and who was permitted to tell it.

The streets, too, were managed and staged.

Along Valiasr Street, where traffic usually performs its daily ritual of impatience and frustration, movement slowed as the roads gradually surrendered to the funeral preparations. Workers built stations to feed and give water to those arriving to mourn him.

Loudspeakers sent chants and laments through the air, and praised the supreme leader who was killed at the onset of the U.S.-Israeli war against Iran.

A little farther away, at Enghelab Square, another version of Tehran moved beneath a giant mourning billboard.

Young women with uncovered hair and cigarettes in hand, and men with pierced ears, crossed paths with conservative women in black chadors carrying Iranian flags and praying quietly. It was an image that seemed to contain the contradictions of Iran itself: a nation Ayatollah Khamenei had shaped for decades, and one that, in his final years, had increasingly pushed back against the boundaries of his oppressive rule.

We lingered for almost two hours at the square, where most people were unwilling to talk to us, wary of foreign media. We asked to interview a woman with blond hair, a dark blue denim skirt, full makeup and a hijab barely resting at the edge of her hair. She smiled softly and said, “I am afraid I won’t be able to say what’s in my heart.”

At the square, some people stopped to photograph the giant statue of a clenched fist. Others kept walking and driving by. Every evening, life continued beneath the preparations, ordinary rhythms folding themselves into something much larger. Street vendors calling out, motorcycles weaving between cars, tea glasses clinking in small cafes.

Beneath the banners and portraits was another Tehran, a city worn by months of pressure.

A regional war with Israel last year compounded a financial malaise exacerbated by sanctions. Those economic frustrations boiled over into mass protests beginning in late December that the authorities crushed, killing thousands. Then came the war with the United States and Israel, taking the lives of young children at school, damaging historic sites like Golestan Palace and leaving residents checking the skies and refreshing news alerts. The past months had seemed to compress multiple eras of strain into a single season.

And states — especially autocratic ones like Iran’s — often answer uncertainty with scale.

So this exhausted capital has suddenly found itself transformed into the stage for a burial spectacle of extraordinary proportions.

At the Grand Mosalla, a sprawling mosque complex in Tehran, tens of thousands arrived this weekend dressed almost entirely in black to pray for and pay their respects to the Shiite Muslim patriarch. They cried and wailed openly. They struck their chests and heads in ritual mourning. Some sat on the ground, weary and stunned.

“Khamenei was the foundation of our lives,” said Mohamed Soleimani, from Tehran, who sat at the mosque’s grounds, head bowed, holding a photo of Mojtaba Khamenei.

Grief also gave way to anger. Fists rose in the air. Chants of revenge filled the space — directed at Israel, at the United States and, repeatedly, at one man whose name was taken up again and again by the crowd: Donald J. Trump.

The funeral, which will continue in the coming days through Tehran, other Iranian cities and even neighboring Iraq, seems designed to do something larger than simply bury a leader.

It is an effort to project continuity at a moment when the country itself seems caught in a period of transition and uncertainty.

So Iran moves forward for now, beneath commemorative banners and enormous portraits of Ayatollah Khamenei, still trying to understand what exactly is ending — and what is taking shape in its place.

Four months after its supreme leader was killed in U.S.-Israeli airstrikes, Iran’s government began a week of elaborate events to mourn and bury Ayatollah Ali Khamenei, sending a message of stability and unity to the world — and to its enemies.

Images published on Friday by Iranian state media showed Iranian and foreign officials, militia members and religious leaders walking to and standing before the casket of Ayatollah Khamenei, who was killed on Feb. 28. Some visitors bowed solemnly, prayed or cried.

It sets the stage for a series of ceremonies, which will continue on Saturday with a public viewing of Ayatollah Khamenei’s casket. After a procession in Tehran on Monday, his body will be taken to holy Shiite cities in Iraq before he is buried in his hometown, Mashhad, in Iran.

The casket, decorated with the Iranian flag, was topped by a black turban and a black-and-white checked scarf like one he often wore, which in Iran is associated with the country’s Basij militia force. The black turban signifies that he was a cleric descended from the Prophet Muhammad.

Friday’s ceremony took place in Tehran’s Grand Mosalla, a large prayer complex where Ayatollah Khamenei gave many important addresses during his reign. State news reports said his casket was surrounded by those of family members who were killed along with him.

By Friday morning, symbols of mourning had spread across Tehran. Giant black banners hung from overpasses and buildings, while billboards bearing Ayatollah Khamenei’s portrait appeared along major roads and intersections.

Some showed him alone, gazing outward in the familiar official imagery that long dominated the country’s political landscape. Others paired him with his son and successor, Mojtaba Khamenei, visually linking the end of one era to the beginning of another.

While Iran’s government is seeking to portray Ayatollah Khamenei as a beloved and respected leader of global stature, many Iranians may view the expensive, dayslong funeral with discontent or anger.

Over 37 years of authoritarian rule, Ayatollah Khamenei harshly repressed dissent and allowed economic mismanagement and corruption to fester in Iran.

The long delays to his burial, more than four months after his killing, reflect the extraordinary circumstances Iran has faced this year: bombardment by the United States and Israel, with uncertainty over whether the government could ensure a secure event.

Mr. Khamenei was a constant presence in Iran’s political life for decades. Some of his supporters said that his killing remained difficult for them to process, and the days of mourning planned across the country have become an occasion to grieve and mark the end of a political era.

The funeral comes at a particularly turbulent moment for Iran. The past six months have left deep fissures in the country, with protests, regional conflict, security tensions and internet shutdowns disrupting daily life and contributing to broader uncertainty and instability. For many Iranians, the death of a leader who had dominated for decades was yet another turning point in a period defined by upheaval.

“I still cannot believe he’s gone,” said Dunya Mohamadi, 24, who was in central Tehran on Friday with her 10-month-old son, Ali. She said she had traveled with her family from Malard, about 24 miles west of the capital, to attend the ceremonies. “My heart wants to mourn as best as I can,” she said.

The New York Times was granted access to the funeral ceremonies of Ayatollah Khamenei by Iran’s government, which determined the ceremonies our reporters could attend, accompanied by a government-provided translator and a guide. The views expressed by people interviewed at these events may not be representative of many Iranians, while others may have felt unable to speak freely.

More than 50 official foreign delegations participated in the viewing ceremony on Friday, a spokesman for the funeral organizers told Iranian state media.

Dmitri A. Medvedev, a former president of Russia and the deputy chairman of its Security Council, is expected to attend Friday’s ceremony, the Kremlin spokesman, Dmitri S. Peskov, said Thursday. Russia has given support to Iran during its war with Israel and the United States, and Iran has supplied drones to Russia that it has used to attack Ukraine.

China is sending a senior Chinese lawmaker, He Wei, who is a vice chairman of its top legislature. Iran is increasingly looking to China as a critical economic partner, and the country has been the primary purchaser of Iranian oil over the last several years.

Leaders of Shiite communities abroad were also in attendance, including from Pakistan. During the six days of public ceremonies that are expected to follow, Iran’s government is seeking to emphasize Ayatollah Khamenei’s role as a Shiite spiritual leader with devoted followings throughout the Muslim world.

Members of several Iranian-aligned militias in Iraq also attended on Friday, including Kataib Hezbollah, according to images published by Iranian state media. The group has attacked U.S. targets in Iraq in recent months. The images also showed family members of slain leaders of the Lebanese militant group Hezbollah, which is backed by Iran.

Iraq’s president, Nizar Amedi, and the country’s speaker of Parliament, Haibat al-Halbousi, were also in attendance for the funeral ceremonies. The arrival of Iraqi officials comes at an awkward moment for Iraq’s new government, as it is under increasing pressure to loosen its ties to Iran.

Ayatollah Khamenei’s funeral has also brought together adversaries, if not outright enemies, who are otherwise engaged in deadly conflicts in the region.

The president of Iraq’s Kurdistan Region, Nechirvan Barzani, met with Iranian officials on Friday, according to Iranian state media. His region hosts Iran’s exiled Kurdish militias, who remain in an undeclared shadow war with Iran’s Islamic Revolutionary Guards Corps. There have been reports by local news outlets in recent days of clashes.

From Afghanistan, one of the Taliban’s most senior figures, Mullah Abdul Ghani Baradar, and its foreign minister, Amir Khan Muttaqi, were set to attend the funeral.

And on Friday, Ahmad Massoud, the son of Ahmad Shah Massoud, a commander who fought the Taliban in the 1990s, could be seen paying his respects. Mr. Massoud now leads one of the main opposition groups to Taliban rule from abroad.

Also scheduled to attend the funeral were Prime Minister Shehbaz Sharif of Pakistan and the country’s army chief, Field Marshal Syed Asim Munir. Their country has been embroiled in a conflict with Afghanistan that has left hundreds dead since late February as Pakistani officials accuse the Taliban of supporting militant groups that have killed thousands of security personnel in Pakistan in recent years.

Pakistan and Iran’s relations have been marred by tensions in recent years, but the war with the United States and Israel, and Pakistan’s role as a mediator to end the conflict, has brought their leaderships closer.

The killing of Ayatollah Khamenei rattled many among Pakistan’s estimated 35 million Shiites, a minority often targeted by militant violence.

The city of Tehran had already begun reorganizing itself on Friday for the large public elements of the funeral in the days ahead.

Officials announced traffic restrictions and heightened security measures before the procession, with police officers and security personnel visible across central Tehran. Many shops in the city center were closed, leaving the typically crowded streets unusually quiet. Roads were closed as the authorities prepared for what they said would be one of the largest public gatherings in the history of the Islamic Republic.

Across the capital, volunteers prepared stations to feed and support the large crowds expected to arrive before public ceremonies were to begin early Saturday. At one such station, Hamid Reza, 54, directed men unloading boxes of food, fruit and supplies from a truck. He said organizers at that location alone expected to distribute some 300,000 bottles of water and had stocked eggs, lentils, watermelons and snacks for mourners.

He described the work as his contribution to honoring a leader he admired.

“We miss him,” he said. “I wish I had sacrificed myself for our leader.”

Elian Peltier, Erika Solomon, Paul Sonne and Li You contributed reporting.