Look for running, biking, and lots of visitors.
Listen for music.

From the festival website:

Dominion Riverrock is the East Coast’s premier outdoor lifestyle festival, bringing athletes, spectators, musicians, and even dogs to Brown’s Island for a two-day festival against the backdrop of Richmond’s downtown riverfront. The party begins on Friday with performances by Big Gigantic and Perpetual Groove, a 5k mud run, and acrobatic kayak and freestyle bike competitions. Then, join in the fun Saturday in high-adrenaline activities both in and around the river – like the James River Scramble 10k trail run, mountain biking, kayaking, Ultimate Air Dogs and much more. The festival culminates with a performance by Yonder Mountain String Band. New to the event in 2011 are bouldering and Stand Up Paddleboarding. With additional musical performances, food, exhibits and more, Dominion Riverrock is a must-do for people of all ages.

Click here for schedule.