The marriage of Crown Prince Hussein, 28, and Saudi architect Rajwa Alseif, 29, drew a star-studded VIP list headlined by Britain's Prince William and his wife Kate, who arrived at the palace and were welcomed by Jordan's King Abdullah II and Queen Rania.

The celebrations hold deep significance for the region, emphasizing continuity in an Arab state prized for its longstanding stability and refreshing the monarchy's image after a place feud. It even could help resource-poor Jordan forge a strategic bond with its oil-rich neighbor, Saudi Arabia.

Crowds were gathering at huge screens set to livestream the wedding across the country, with many attendees waving flags and decked out in the white-and-red checkered scarves worn by Jordan's ruling family, the Hashemites.

At the ancient Roman amphitheater in the center of the capital, Amman, Jordanian singer Hussein Salman pumped up the crowds with congratulatory wedding ballads. The 6,000-seat theater was almost completely full, as families sang along and children, with “Celebrating Hussein” painted on their cheeks, clapped wildly.

“This is an important day because he is our future king,” said Ahmad al-Masri, an 18-year-old attending with his family. “All of Jordan is watching.”

World leaders and royalty are also attending. William and Kate arrived early Thursday on a visit that had been kept under wraps. It was only confirmed by Jordanian state media a few hours before the start of the palace ceremony.

On Thursday morning, Saudi wedding guests and tourists — the men wearing white dishdasha robes and the women in brightly colored abayas — filtered through the sleek marbled lobby of the Four Seasons Hotel in Amman. Noura Al Sudairi, an aunt of the bride, was wearing sweatpants and sneakers on her way to breakfast.

“We are all so excited, so happy about this union,” she said. “Of course it’s a beautiful thing for our families, and for the relationship between Jordan and Saudi Arabia.”

Excitement over the nuptials — Jordan’s biggest royal event in years — has been building in the capital of Amman, where congratulatory banners of Hussein and his beaming bride adorn buses and hang over winding hillside streets. Shops had competing displays of royal regalia. Royal watchers speculated about which dress designer Alseif would select— still an official secret.

“She looks like such a princess that I think she deserves him,” Suhair Afaneh, a 37-year-old businesswoman, said of the bride, lingering in front of a portrait of Hussein in a dark suit. “But so what, I’ll still be in love with him.”

Jordan’s 11 million citizens have watched the young crown prince rise in prominence in recent years, as he increasingly joined his father, Abdullah, in public appearances. Hussein has graduated from Georgetown University, joined the military and gained some global recognition speaking at the U.N. General Assembly. His wedding, experts say, marks his next crucial rite of passage.

“It’s not just a marriage, it’s the presentation of the future king of Jordan,” said political analyst Amer Sabaileh. “The issue of the crown prince has been closed.”

The wedding may create a brief feel-good moment for Jordanians during tough economic times, including persistent youth unemployment and an ailing economy.

Palace officials have turned the event — a week after Jordan’s 77th birthday — into something of a PR campaign. Combining tradition and modernity, the royal family introduced a wedding hashtag (#Celebrating Al Hussein) and omnipresent logo that fuses the couple’s initials into the Arabic words “We rejoice.”

Photos and reels from Alseif’s henna party — a traditional pre-wedding celebration featuring the bride and her female friends and relatives — and the couple’s engagement ceremony in Saudi Arabia last summer, have splashed across state-linked media.

The kingdom declared Thursday a public holiday so crowds of people could gather after the wedding service to wave at the couple’s motorcade of red Land Rover jeeps — a nod to the traditional procession of horse riders clad in red coats during the reign of the country’s founder, King Abdullah I. Tens of thousands of well-wishers are expected to flock to free concerts and cultural events. Huge screens have been set up nationwide for crowds to watch the occasion unfold.

The signing of the marriage contract will take place at Zahran Palace in Amman, which hasn’t seen such pomp and circumstance since 1993, when, on a similarly sunny June day, Abdullah married Rania, who was born in Kuwait to Palestinian parents.

Decades earlier, Abdullah's father, the late King Hussein, sealed his vows in the same garden with his second wife, the British citizen Antoinette Gardiner.

In addition to the Prince and Princess of Wales, the guest list includes an array of foreign aristocrats and dignitaries, including senior royals from Europe and Asia, as well as First Lady Jill Biden and U.S. climate envoy John Kerry. Other likely attendees include Saudi aristocrats, as Alseif’s mother is related to the mother of Saudi King Salman. Her billionaire father owns a major construction firm in the kingdom.

After the ceremony, the wedding party will move to Al Husseiniya Palace, a 30-minute drive away, for a reception, entertainment and a state banquet. The royals are expected to greet more than 1,700 guests at the reception.