After years of delays, the 26-acre Hudson Yards site, Manhattan's single-largest undeveloped property and New York City's largest private development since Rockefeller Center, broke ground on its first building today, Dec. 4. Led by general contractor Tutor Perini and builder Tishman Construction, work on the $1-billion-plus, 47-story South office tower at 10th Ave. and 30th St. is set for completion in 2015.

The 1.7-million-sq-ft, mixed-use tower, designed by New York-based Kohn Pedersen Fox Associates, is part of a planned $15-billion complex to be built over a Long Island Railroad storage yard. Other planned structures on the site include a 2.4-million-sq-ft north tower; a cultural facility; hotel; public school; office space; residences; retail shops; and open space with access to the waterfront. Officials say that development of the yards will create nearly 23,000 construction jobs.