Charlotte Mecklenburg Library's main library uptown will be demolished in two years and replaced with a new five-story building expected to open in 2024. Officials unveiled the design Thursday for a $100 million building at North Tryon and Sixth streets that includes a ground-floor cafe, outdoor terraces on the second floor and roof, and a curved block of upper floors.

The current two-story library was built in 1989 and in need of an upgrade or replacement, said library CEO Lee Keesler.

"Modern libraries have lots of spaces for people to convene, to meet, to work together -- much more technology in today's libraries," Keesler said. "So it's just time to upgrade the facility for our community."

The $100 million cost will be paid for with public and private money. Library officials Thursday also announced a $135 million campaign to pay for the new building as well as technology and other library system projects. They're 67 percent of the way there, with about $90 million raised so far in the campagn's quiet phase. That includes commitments of $65 million from Mecklenburg County and $10 million from the Knight Foundation - its largest local gift ever.

Library officials have been talking for years about renovating or replacing the building. Keesler said Snohetta, the architecture firm that did the design, studied a renovation. But in the end, a new building made more sense.

The new library is the latest in a series of projects as part of the broader North Tryon Vision Plan. Others include a major overhaul at Discovery Place and a 34-story hotel tower that the Foundation for the Carolinas is building atop the old Carolina Theatre.