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.

"We are over 80% committed to the first commercial tower," says Stephen Ross, chairman of Related Cos., co-developer of the yards along with Oxford Properties Group. Besides luxury retailer Coach Inc., the first tower's anchor tenant, two other, unspecified tenants have been secured, Ross says. He adds that Hudson Yards, when completed, will be Related's new home as well as his personal residence.

The Metropolitan Transportation Authority (MTA), which is leasing the land to the developers, is extending the No. 7 subway line close to the site. Both the project and the subway extension will "revolutionize" the West Side of Manhattan and spur further development, says Joseph Lhota, MTA chairman and CEO.

Earlier this year, construction began on the third and final section of the High Line elevated rail line project, which will extend into Hudson Yards.