The sixth annual Tour of Lawrence takes off this weekend, with more than 600 professional and amateur bicycle racers and enthusiasts expected in town Friday through Sunday.

The USA Cycling-sanctioned, Pro-Am event, presented by US Bank and made possible by the Lawrence Convention and Visitors Bureau, features street sprints, circuit races and a criterium.

Organizers say this year’s theme — “So you think Kansas is flat, think again!” — highlights the challenges of the course.

The Sunflower Outdoor & Bike street sprints begin at 7 p.m. Friday on Vermont Street and include the free Kids’ Zone, followed by live music by Hearts of Darkness.

On Saturday, the Meadowbrook Apartments Kansas University campus circuit races are from 8:30 a.m. to 4 p.m. They take cyclists on a loop course of the KU campus, with some race distances covering 55 miles. The circuit course includes the climb up Mississippi Street to Memorial Drive and downhill on sections of Emery Road and Ninth Street.

Sunday features the Free State Brewery Downtown criterium beginning at 8 a.m. for a nearly one-mile loop course that will bring riders along Vermont, Massachusetts and New Hampshire streets.

Events for the kids begin with the Kids’ Zone downtown on Friday evening and again Sunday morning with a bounce house and inflatable games. For the little riders with big ambitions, there is a free bike race for kids Sunday morning at the library plaza on Vermont Street. Registration begins at 9:30 a.m., and the race is at 11 a.m. The competitive races for adults begin at noon.

Races are free for spectators. The public is invited to line the streets of the race courses and see some of the top names in competitive racing. The races are well-timed with the Free State Festival, as the riders and spectators can take advantage of the Lawrence Arts Center’s films and activities after the races.

To register or for more information, visit touroflawrence.com or Tour of Lawrence’s Facebook page.