Denver streets will be clogged Sunday with 12,000 runners, walkers, and spectators for the Rock 'n' Roll Denver Marathon, including Arapahoe St, Auraria Pkwy, Speer Blvd, Wazee St, and others.

A majority of road closures and detours will begin at 6:15 a.m., lasting as late as 2:30 p.m. Pedestrians and bicyclists will still be able to cross the roads, but only during gaps as to not interfere with race participants.

The half marathon and 10K begins at 7:15 a.m., the marathon will begin at 8:00 a.m., and the 5K will start at 8:05 a.m.