Where the world goes from the excitement of watching Michael Phelps wreck medal records to the fervent anticipation of watching Usain Bolt beginning his campaign to write his own history.
His incredible legacy culminating with a 28th medal, 23 of which are gold -- more than all but 39 countries.
"It's been an honor to be on two Olympic teams with him. Last time was his last, this team is his last, so I get to say I was on Michael Phelps last Olympics two times which is cool, maybe there'll be a third time," US phenom Katie Ledecky said.
Phelps, who has swum in five Olympics, said no. His swimming career is over.
"It's not the end of a career, it's the beginning of a new journey," he told NBC.
For clarity's sake, there is one more set of swimming events, but the marathon (10 kilometers) events are set in the water off Copacabana Beach.
For Bolt, the day was the start of his attempt to become the first man to win the three track and field sprint events
-- the 100 meters, the 200 meters and the 4x100 meters relay -- in three Olympics.
The 29-year-old came into the Olympics having missed the Jamaican national championships with a bad hamstring.
All seemed well Saturday. Despite a rough start, he still ran 10.07 to win his qualifying heat in the 100.
Here are other memorable moments from Saturday's action:
Another historic moment for a US woman
These Games have been full of milestones for women representing the United States and Ibtihaj Muhammad is the latest to achieve a notable first.
The 30-year-old from Maplewood, New Jersey, became the first US athlete to wear a hijab and win an Olympics medal.
and her three teammates won bronze in the women's team saber event, downing Italy by a comfortable 15 points. Muhammad drew her first match 5-5 and won her second 5-3.
Teammate Mariel Zagunis became the first US fencer to medal at three Olympics.
Puerto Rico's golden moment
Add US territory Puerto Rico to the list of first-time gold medal winners, thanks to tennis star Monica Puig
"It's just amazing. I know my country really appreciates this and I really wanted to give this victory to them," Puig said. "And the way I did this victory tonight, I wouldn't want it any other way."
She later tweeted: "We did it Puerto Rico!!!!!!!!!"
Puig defeated world No. 2 Angelique Kerber of Germany in singles, two sets to one.
Puerto Rico had won just eight Olympic medals -- six bronze and two silver -- prior to Puig's success. Six of those were won in boxing.
Puerto Rico joins Fiji, Kosovo and Singapore as national Olympic committees that have won first-ever gold medals in Rio.
And then there were none
Russia's athletics team won 18 medals four years ago, eight of them gold. But things will be vastly different in Rio due to a doping scandal.
The traditional powerhouse had most of its Rio squad banned as a penalty for doping but it did manage to get one US-based competitor into the 2016 Games.
But now she's barred too
. Long jumper Darya Klishina says people with a political agenda are behind her suspension by the International Association of Athletics Federations. She swears that she is clean.
She's appealing her suspension and hopes to compete in the first rounds of the event Tuesday.
"I will take every possible effort to protect my clean image as an athlete," she said in a statement on Facebook. "At this moment I cannot help but feel betrayed by a system that is not focused on keeping the sport clean and supporting rank-and-file athletes, but rather seeking victories outside sport arenas."
One green pool drained
The Rio 2016 local organizing committee has decided to drain the green water in the competition pool at the Maria Lenk Aquatics center.
Organizers blamed the addition of 80 liters (21 gallons) of hydrogen peroxide.
Rio 2016 director of venue management Gustavo Nascimento said the work should be done by Sunday morning, just a few hours before the start of synchronized swimming.
"We have been trying to clean the pool for four days and obviously it's not going as fast as we want it to," Nascimento said.
The adjacent diving well will not be drained, because there haven't been many complaints from the athletes. A filter adjustment should help change the color of the water from green to light blue.
Workers will drain the pool, which also has been the site of water polo, and fill it with water from a warmup pool.
Nascimento said the hydrogen peroxide was not a danger to the athletes but blunted the chlorine's ability to "kill organics."
Gold medal roundup
Winners of the other medal finals Saturday:
Athletics, Men's 10,000 meters -- Mo Farah, Great Britain
Athletics, Men's Discus -- Christoph Harting, Germany
Athletics, Men's Long Jump -- Jeff Henderson, United States
Athletics, Women's 100 meters -- Elaine Thompson, Jamaica
Athletics, Women's Heptathlon -- Nafissatou Thiam, Belgium
Fencing, Women's Team Saber -- Russia
Rowing, Men's Eight -- Great Britain
Rowing, Men's Single Sculls -- Mahe Drysdale, Australia
Rowing, Women's Eight -- United States
Rowing Women's Single Sculls -- Kimberly Brennan, Australia
Shooting, Men's Rapid Fire Pistol -- Christian Reitz, Germany
Shooting, Men's Skeet -- Gabriele Rossetti, Italy
Tennis, Women's Singles -- Monica Puig, Puerto Rico
Trampoline Gymnastics, Men -- Uladzislau Hancharou, Belarus
Track Cycling, Women's Keirin -- Elis Ligtee, the Netherlands
Weightlifting, Men's 94 kilograms -- Sohrab Moradi, Iran