The first day of the rest of Michael Phelps’s life broke Sunday morning after maybe four hours of sleep, even though there was no pool to go to, no practice to endure. He took a car from his hotel — a former athlete in every sense of the phrase, he has moved out of the Olympic Village — and saw, for the first time since he arrived here, Big Ben, Parliament, London’s skyline.

The blinders are off. Now what?

“This is sort of my first day,” Phelps said. “I don’t know what to do.”

At this, the end of his fourth and final Olympics, Phelps has wrung every last superlative from the washcloth. What more, after 22 medals, 18 of them gold, is there to ask? What more can he say?

Yet when he hosted a news conference Sunday, an event staged by Visa at an ornate convention center steps from Westminster Abbey, he faced a wall of 30 cameras behind a packed room of journalists. He took questions from Brazil and Colombia, from Australia and Nigeria, from China and Turkey. But in a way, the most compelling items Phelps had to offer were the questions he spat back.

“Who knows what’s going to happen?” he said.

This is a man who has thought of little other than swimming for 20 years — save for a few touch-and-go-moments in the past four years, when his coach wondered if he would focus enough to end up in London. Yet now, after winning more Olympic medals than any athlete in history, he says he is done with his sport. He said Sunday he intended to take a vacation, to travel the world.

“Who knows where I go?” he said.

These seem to be genuine questions from an athlete, a person, who is clearly undergoing a metamorphosis at age 27. As he overcame an ominous start to his meet here, his first Olympic race without a medal since his first Olympics in 2000, teammates frequently spoke of a more open, more giving compatriot. In 2008 — when he won a record eight gold medals, changed his sport and began shaping his own legacy — he seemed programmed, mechanical. The task was so daunting, there was perhaps no other way to undertake it. Here, though, he was human, first in defeat, and then in winning six more medals, the final four gold.

“You’re going to make me tear up,” said five-time London medalist Allison Schmitt, who trained with Phelps at the North Baltimore Aquatic Center for the year leading up to these Games, when she was asked earlier in the week about Phelps. Saturday morning, Phelps and Schmitt held hands as they plunged into the pool for the final practice of Phelps’s career.

“I’m speechless,” Schmitt said. “Being able to see him after the race, I feel like I want to jump him and give him a hug every time. He makes me tear up every time I see him. I couldn’t be happier to be his teammate and his friend.”

Those who are with him the most saw the changes. Peter Carlisle of Octagon became Phelps’s agent when he was just 17. More than anyone, he knows that Phelps’s responses to public queries over the past decade could be rote, mundane. The Phelps who spent this past week in London felt different.

“Here it’s very much been he’s enjoying it, reflective, thoughtful,” Carlisle said. “It’s funny. You can imagine, the questions that you hear; it’s the same questions over and over. Normally, he’s getting impatient, and I know all the answers he’s going to give before he says them.

“It’s totally different now. It’s like he’s processing this stuff now. So even if it’s the same question, he’s feeling something. He’s feeling a little bit different than he did yesterday. It’s 10 years of stuff that’s changed his perspective.”

Carlisle has spent the past decade building endorsement contracts with an eye on this moment: the first day after he was done as a competitor and turned into an old-timer.

“From my view, I think he’s one of the handful of truly global sports icons,” Carlisle said. “In Beijing, he solidified his recognizability throughout the world. He solidified his relevance throughout the world, just with the uniqueness of what he did. But these Games, he solidified his legacy.”

So expect more commercials, more ads, more exposure, even as he transitions to a non-competitive lifestyle. Phelps said Sunday he intends to improve his golf game. He will not, he said, treat his body as he did following the Beijing Games, when he gained 25 pounds, a release after a focus so intense it became stifling. That kind of thing led to the questions about how he would perform in London.

“There were just plenty of times where he maybe wasn’t at practice for a couple weeks,” his coach Bob Bowman said, “and I’d wonder if we were going to get this done.”

They got it done, and more. Now, the hard part: Phelps still has a competitive mind, is still a swimming junkie. Late Saturday night, after a party with family and friends, he settled into a London hotel. There, he sat down with Lenny Krayzelburg, a four-time gold medalist backstroker who was Olympic teammates with Phelps in 2000 and 2004. The chatter? Swimming, of course — different times in different races, world records and medals, disappointments and characters.

Maybe, less than 24 hours removed from the pool, Phelps couldn’t rightfully be expected to be cleansed of it. But the day after his career ended, there seemed to be no easy answer to what the next stage will bring.

“Who knows where this leads me?” Phelps said. “This is my first day of retirement, and the first day of the rest of my life.”