A half-mile-long section of King Street will be closed off May 16 so cyclists and pedestrians can have the street to themselves.
The event, billed as "Do the Charleston," aims to create a family fun day along the city's main commercial street, from noon to 5 p.m.
Earlier that Sunday, two groups of cyclists will make bike trips from the Isle of Palms and Folly Beach to downtown.
That morning ride, organized by the cycling advocacy group Charleston Moves, will highlight its "Battery to the Beach" effort to improve bike lanes in six cities between downtown and its closest beaches.
Jamie Price, a developer and artist who worked for six months to get the city's permission for the "Do the Charleston" event, said other cities occasionally close downtown streets for cyclists and pedestrians.
He said closing the street between Calhoun and Queen streets will attract parents with children and other cyclists who otherwise might feel uncomfortable riding in traffic.
"Downtown is a great place to cycle on a Sunday," he said. "We have King Street closed, but it's fantastic to cycle around the peninsula on Sundays and see things. Or people can just walk, whatever."
Meanwhile, cyclists also will have a chance to ride as a group from the beaches to downtown from 10-11:30 a.m. May 16, said Kristin Walker, a real estate agent who serves on the board of Charleston Moves.
The Folly ride will begin from the small park at the entrance to the island, while the Isle of Palms ride will begin from the Red and White grocery.
Planning for that ride began separately from the King Street closure, but Walker said, "We thought they were a perfect complement to each other."
Tom Bradford, director of Charleston Moves, said he hopes the beach-to-downtown rides will grow in frequency and number to encourage Charleston, Mount Pleasant, James Island, Folly Beach, Sullivan's Island and the Isle of Palms to do more to make the ride more safe and more fun.
"We might actually get officials to participate and sign some sort of document where they're pledging to do an expeditious job on this," Bradford said.
Price said he also hopes the "Do the Charleston" event becomes a more frequent type event on King Street. "I'm hoping it could be several times a year," he said. "That's the goal."
The King Street closure is rare but not unprecedented. The city used to close King between Wentworth and Market streets during the Christmas season, but that stopped when the city moved the focus to Marion Square.
The "Do the Charleston" event will include entertainment from White Tuxedo Productions, and restaurants will be allowed to expand their operations into onstreet parking spaces. Other food vendors will set up just south of Market Street.