DIRIYAH, Saudi Arabia » More than 250 years ago, in this sunbaked oasis of mud-brick houses and ramparts, the ancestors of the Saudi royal family and an outcast fundamentalist preacher formed an alliance that has shaped this land ever since.

In return for political supremacy, the House of Saud endorsed the doctrine of Sheikh Muhammad ibn Abdul-Wahhab and followed it to wage jihad against anyone who rejected their creed, gaining control of much of the Arabian Peninsula.

That alliance laid the foundations of the modern Saudi state, which has in more recent times used its oil wealth to make the cleric’s rigid doctrine – widely known as Wahhabism – a major force in the Muslim world.

And now, this site, the birthplace of it all, is becoming a tourist attraction.

Inside a massive complex on the outskirts of Riyadh filled with parks, restaurants and coffee shops, hundreds of laborers are rehabilitating mud palaces once home to the Saud family and building museums celebrating its history. Nearby stands a sleek structure that will house a foundation dedicated to the sheikh and his mission.

The project comes at a tough time for Saudi Arabia. Popular revolts and civil wars have shaken the regional order; the drop in oil prices has hit the national budget; and the kingdom is once again being accused by many of promoting an intolerant brand of Islam similar to that of the Islamic State.

But the kingdom is doubling down on its origins. The development of Diriyah is a pet project of the new king, Salman, who is seeking to create a showcase attraction to reinforce the royal family’s national narrative. The entire complex is expected to open in two years at a total cost of about a half-billion dollars, according to a contractor who declined to be named because the sum has not been made public.

Saudi officials hope the project will link citizens to their past and rehabilitate the reputation of Abdul-Wahhab, which they say has been wrongly sullied.

While Wahhabism has adherents around the world, many Muslims detest it, because it considers Shiites and followers of other non-Sunni sects – not to mention Christians and Jews – to be infidels. Others blame Saudi Arabia’s promotion of Wahhabism abroad for giving theological fuel to groups like al-Qaida and the Islamic State, an accusation Saudi officials reject.

"It is important for Saudis who are living now, in this century, to know that the state came from a specific place that has been preserved and that it was built on an idea, a true, correct and tolerant ideology that respected others," said Abdullah Arrakban of the High Commission for the Development of Riyadh that oversees the project.

The planned Abdul-Wahhab foundation is to be an international study center, showing the importance Saudi Arabia still puts on spreading the sheikh’s teachings.

However, many scholars say that the cleric was not known for his tolerance.

"If someone else did not agree with his conception of monotheism, they had to either convert or be conquered," said David Commins, a history professor at Dickinson College in Carlisle, Pennsylvania, who has written a book on Wahhabism.

In the 18th century, that sense of divine mission gave the House of Saud an advantage in the tribal battles that rocked the Arabian Peninsula.

"When you throw a theological reform movement into the mix you create an ideological foundation for people here and there to support the Saudi banner rather than another chieftain," Commins said.

Some found the ideology appealing and accepted Saudi leadership. Others resisted and were deemed "polytheists" who had strayed from monotheism, perverting the one true faith, and needed to be corrected.

These included other Sunni Muslims who practiced different versions of the faith as well as Shiites, thousands of whom were slaughtered when Saudi forces sacked Karbala, in modern-day Iraq, in the early years of the 19th century, Commins said.

After the House of Saud extended its control over the holy cities of Mecca and Medina, the Ottomans struck back, toppling the first Saudi state and destroying its capital in Diriyah. Surviving members of the family moved to Riyadh, where King Abdul Aziz Ibn Saud, Salman’s father, founded the modern Saudi state in 1932. He also re-established the alliance with Sheikh Abdul-Wahhab’s descendants, which endures to this day.

Many Saudis reject the term Wahhabism, saying the sheikh did not create a new ideology, but restored the original teachings of Islam by stripping away additions like the veneration of saints.

Nothing should be celebrated except God, he taught, leading his followers to destroy saints’ tombs and reject national holidays and birthdays.

Some critics say the interest in Diriyah by the kingdom’s rulers is more about politics than about historical preservation, noting that the government has neglected or destroyed many other heritage sites.

Ottoman buildings have been scrapped or left to collapse, and researchers struggle to get permits to visit relics of historic Christian settlements.

The Wahhabi fear that any relic could itself become an object of worship has led to the destruction of more than 95 percent of the historic sites near the holy cities of Mecca and Medina, according to Irfan al-Alawi, director of the Islamic Heritage Research Foundation.

Scores of tombs have been destroyed; a house associated with Muhammad’s first wife, Khadija, was replaced with a bank of public toilets; and a home believed to have belonged to his companion Abu Bakr was razed to make way for a Hilton Hotel, al-Alawi said.

At the same time, the Saudi government has filled Mecca with increasingly modern buildings that include the world’s third tallest building and, soon, its largest hotel.

Madawi al-Rasheed, a visiting professor at the London School of Economics who has written books on Saudi history, said the royal family tries to bolster its legitimacy by creating "historical amnesia" about aspects of the kingdom’s past that do not relate to its rule.

"Diriyah is extremely important in this because for the Saud, it all started there and they want to say that the Arabian Peninsula had no history before them," Dr. Rasheed said.

The site has changed dramatically in recent decades. After the city lay abandoned for centuries, families moved in in the mid-1900s and built new mud-brick homes. The government bought the site in 1982 and the development program began around 1990, when King Salman was the governor of Riyadh province.

The king remains among the development’s champions and has built a palace next door where he spends his weekends. Visitors to the site can see his convoy enter on Friday and return to Riyadh on Saturday.

The complex will feature parks, restaurants, underground parking and a series of museums about traditional Saudi life, warfare and the Arabian horse. Visitors will also be able to stroll through the old mud settlement, Turaif, which was named a UNESCO World Heritage site in 2010; shop in a traditional market; and sleep in a boutique hotel.

On a recent evening, footpaths snaking between restaurants and coffee shops filled with children playing and riding bicycles, while families picnicked under date palms.

"It is nice to have something like this in Riyadh because it looks like a desert," said Saleh al-Mohaya, who was strolling with his wife.

Others came for the history.

"France is based on the revolution, America is based on the Founding Fathers and Saudi Arabia is based on the mission of Sheikh Abdul-Wahhab," said Turki al-Shathri, scion of a prominent clerical family who said he visits often.

He dismissed any suggestion that Abdul-Wahhab was intolerant or had anything in common with the Islamic State.

Wahhabi theology does not promote the caliphate, he said, and preaches obedience to rulers, not jihad to overthrow them.

"Look around," he said, gesturing at Saudi families strolling and eating ice cream. "Where is the extremism and the terrorism?"

© 2015 The New York Times Company