Cycling fans lined the streets for the first stage of the Tour of Britain as Geraint Thomas rode in Wales for the first time as Tour de France champion.
The race started at Pembrey in Carmarthenshire and featured four-time Tour de France winner Chris Froome.
Rolling road blocks were put in place along the route and organisers warned roads "would be busy".
The stage finished at about 15:20 BST in Newport and was won by German rider Andre Greipel.
Thomas has already had a formal homecoming after becoming the first Welshman to win the Tour de France earlier this year when 8,000 fans lined the streets of Cardiff.
Now the double Olympic track champion and multiple Grand Tour winner Froome have raced for Team Sky on the roads around south Wales.
The race started at Pembrey Country Park at 11:00 BST, and included three intermediary sprints in Carmarthen, Llandovery and Usk before the final sprint finish in Newport.
Carmarthenshire council and Newport council both warned of road closures throughout the day.
The stage finished outside the University of South Wales' Newport city campus on Usk Way and the car park at the nearby Friars Walk Shopping Centre both reopened on Sunday evening.
Organisers warned fans taking selfies "that turning your back on the race is never a good idea" as riders pass "very fast".
"We encourage everyone to get behind the riders, but please remember this is their race," race chiefs said in a statement.
"Don't block their route, run alongside them or impede their progress."
Mark Cavendish, who has won 30 Tour de France stages, and German multiple Tour de France stage-winner Marcel Kittel are both missing this year's eight-stage Tour of Britain.
Former world champion sprinter and Olympic medallist Cavendish, who won a Tour of Britain stage in Wales in 2013 when the fourth leg ended in Llanberis, is ill.
But multiple Grand Tour stage-winners Andre Greipel of Germany and Slovenia's Primoz Roglic, who finished fourth at this year's Tour de France, are competing.
Although a Tour of Britain stage has passed through Wales in each of the last eight years and ended in Cardiff in 2017, it is the first time the tour has started in Wales since the race began in 1945.
On Saturday, Thomas and Froome warmed up for the race by training with their Team Sky teammates and about 175 children in Maindy, Cardiff - where Thomas got the cycling bug as a child riding with the Maindy Flyers Youth Cycling Club.