PLANNED HIGH-RISE: An architectural rendering of the hotel and residential tower at the Los Angeles Convention Center.

The remaking of downtown Los Angeles will gain a crucial missing piece today when developers unveil plans for a 1,000-room hotel complex — including a five-star Ritz-Carlton and a four-star Marriott Marquis — for the Convention Center. Rising 54 stories, the $750-million project would be one of the largest buildings in Los Angeles at 2 million square feet.

The proposed 124-room Ritz-Carlton would be the first five-star hotel downtown and, with the largest ballroom in the city, the planned 876-room Marriott Marquis would fill a void as a business meeting hub at the Convention Center. The hotels are to be topped by 216 luxury condominiums.

The project, scheduled to open in 2010, would anchor L.A. Live, the 27-acre sports-entertainment complex considered the linchpin of downtown's redevelopment.