Organizers say they expect hundreds of thousands of people to attend a series of events over the next week as part of the Aquatennial festival in Minneapolis.
One of the biggest events, the beach bash, takes place at Lake Calhoun on Sunday. It includes races between boats made of milk cartons, as well as a sand castle competition.
The sand castle competition has categories for families and for professional artists, said Aquatennial spokeswoman Elizabeth Kitt.
"The sculptures can range from anything from your standard sand castle on the beach to sculptures inspired by different movies or different parts of Minneapolis," Kitt said. "They can be flat, they can be 3-D; it's very open to interpretation, which lends itself to lots of fun final products."
Two new events at the festival will take place on Saturday -- a music festival at Midtown Global Market and a walk at Lake Calhoun to raise awareness about adults living with mental illness.
The festival's other main events include the Torchlight Parade on Wednesday in downtown Minneapolis and a giant fireworks show next Saturday along the Mississippi River.