There are warnings of travel disruption and road closures as 30,000 runners are expected to take part in the Cardiff Half Marathon on Sunday.
The 23rd edition of the race will see participants run past landmarks including the Wales Millennium Centre and the Principality Stadium.
A variety of bands and choirs will perform along the course, providing entertainment for both runners and supporters.
Widespread road closures are in place to accommodate the 13.1 mile (21km) route, with the race due to start on Castle Street at 10:00 BST.
With high demand for the event, it sold out after going to a ballot for the first time last year, and no on-the-day entries will be available.
Cardiff Half is part of the SuperHalfs series, along with Lisbon, Prague, Berlin, Valencia and Copenhagen.
Runners are challenged to complete the six races in order to earn a SuperMedal.
The event also holds a World Athletics Elite Road Race label and will feature competitors from Kenya, Ethiopia, USA, Australia and the Netherlands.
Former world record holder Joyciline Jepkosgei – the first athlete in history to run under 65 minutes for a half marathon – will headline the women’s field while Gideon Kiprotich is the fastest athlete registered in the men’s field.