Chef Eric Ziebold, foreground, at CityZen with his kitchen staff. (Bill O'Leary/Washington Post)

First-timers and regulars alike, they came to celebrate the past and ponder the future. They came to get one last taste of Eric Ziebold’s food at CityZen, the soaring minimalist, four-star restaurant inside the Mandarin Oriental, and to consider what lies ahead for the chef and fine dining in the District.

For 10 years after he arrived from Thomas Keller’s Per Se in New York, Ziebold help set the tone for formal, chef-driven cuisine in Washington, combining French techniques and a world of ingredients to push his food forward, without relying on the laboratory chemicals and high-tech instruments of the modernists. As Saturday night turned into Sunday morning, though, the restaurant that Ziebold spent a decade refreshing and refining into a dining destination suddenly faded to black, its pilot light permanently extinguished.

The final service at CityZen was routine and irregular. Ziebold didn’t want to take extra reservations or pack his front bar with bodies. He wanted those who had booked reservations for the final night — some securing tables before Ziebold announced the closing in October — to enjoy the standard experience. An important moment in Ziebold’s career would not overshadow the food and service on which CityZen had built its reputation.

The kitchen prepared meals for 96 guests, about the number who usually dine on a Saturday. The diners included such regulars as Kwok Lee, co-owner of a Temple Hills egg-roll company, and his wife, Marion, who were among the precious few to taste-test Ziebold’s cooking before CityZen opened in September 2004.

“We’ve come back once a month at least,” Kwok Lee said. “It gets better every time.”

Eric Ziebold (Sean McCormick/For The Washington Post)

Saturday’s menu was not some CityZen greatest-hits package, cobbled together from a decade of dishes, but essentially the same one Ziebold composed the night before, with a bonus course or two. The largesse was generous and practical. “There’s not a huge benefit to throwing everything in the trash,” the Iowa-native chef said while prepping for the last service. “We might as well use it.”

But Ziebold did offer diners a tiny homage to his time at the Mandarin: an extra mushroom fritter canape — a bite that Ziebold created for his first CityZen menu. Remaining true to his self-effacing Midwestern roots, Ziebold did not tell diners the story behind the freebie, although some knew it. Such as Frank Ruta, chef and owner behind Palena, another D.C. dining institution that closed this year.

Ruta was sitting at the bar with Maddy Beckwith, chef-at-market program coordinator at FreshFarm Markets, and Aggie Chin, former Palena pastry chef. Although she had staged one night at CityZen, Chin had never dined there. Until its last service.

“It is like being here for Christmas,” Chin said. “It’s special, because it is the last time that you can ever dine here.”

Like many on this evening, Ruta presented Ziebold and his team with wine, as a small thanks for all the gustatory pleasures the chef had created. Guests at a table for 12, parked directly in front of Ziebold in the open kitchen, kept bringing him samples from bottles they had brought — wine popped not only to celebrate CityZen’s long reign, but also to fete a birthday boy at the table.

Diners and sommelier David Kurka gleefully ignored CityZen’s usual corkage fees and bottle limit (one!). (The exquisite bottles for the farewell included a 1964 Remoissenet Pere et Fils burgundy, a 1992 Haut-Brion blanc, a 1990 Dom Perignon, a 1996 Lafite-Rothschild, a 1982 Mouton Rothschild and on and on. Most of those bottles came from cellars outside the restaurant; the bottles still at CityZen will remain in the hands of the Mandarin, Kurka said, and could go to auction.)

A number of diners made the unusual trek to the kitchen to congratulate Ziebold for his decade of excellence — and to wish him well with his next venture, a still-unnamed project on Seventh Street NW in Mount Vernon Square. The well-wishers included chefs, wine specialists, longtime patrons and a retired fire chief from Montgomery County.

“I will follow [Ziebold] wherever he goes,” said the former fire chief, LeRoy Oettinger.

“I’m going to call you when I need to pass fire inspection.” Ziebold joked back. Well, maybe he was joking.

The guest list for the night underscored a curious truth about CityZen: It was rarely a destination for celebrities, politicos or the casual foodie types who Instagram their every bite. It was a place for those with thick wallets and a taste for the full-throttled, full-service experience of a fine-dining restaurant. The biggest celebrity in CityZen’s history, Ziebold mentioned, was probably Paul Stanley, the frontman for Kiss.

“He once ate here two nights in a row,” Ziebold said. “I can’t say enough good things about him.”

CityZen’s closing caused more than a few diners Saturday to fret about the state of fine dining in the Washington area. Many had difficulty naming the places left standing — such temples as Marcel’s, Restaurant Eve and Plume at the Jefferson Hotel.

From the tone of Adriaan Rad­der, general manager at the Mandarin Oriental, the hotel doesn’t plan to replace CityZen with another fine-dining destination. Although no decision has been made, Radder said the hotel is considering “less of a special-occasion restaurant.”

Jeffrey Buben, chef and owner behind Bistro Bis and Vidalia (where Ziebold served as a cook in his early years), said that his former employee has re­imagined fine dining once with CityZen and that he will do it again with his next project.

“He’s going to define the new era of fine dining,” said Buben, who supped at CityZen on its final night.

In the meantime, Ziebold wanted to celebrate those who had kept CityZen vital for years. After the last meals were fired and the kitchen had packed away its knives, some on hand lit sparklers or began banging on pots and pans while parading through the dining room, where a few guests lingered well past midnight. Ziebold stood on a chair, raised a champagne glass and thanked his staff — the same staff that had stayed with him to the final day, even though they could have easily found jobs elsewhere.

“As soon as they see CityZen on my résumé, they started calling me and calling me,” said Carlos Villaverde, a back server who will start work at the Source. “I had seven offers.”

To some loyal diners and staff, Ziebold passed out gifts, including those rectangular wooden boxes that have kept the chef’s famous Parker House rolls warm. The question had to be asked: Will Ziebold continue to bake the rolls at his new place, whenever it opens? He laughed appreciably.

“We have that debate all the time,” Ziebold said. “There’s pros and cons to it, and I’m not going to answer that question.”