The Main Station Building (主站房) of the current "New North Station" began construction in 1986 and was commissioned for operation in December 1990, and became one of the five most important railway hubs in China, earning itself the nickname "Northeast's No. 1 Station" (东北第一站).[96][97] In 2011, a huge expansion project known as the "North Station Transport Hub Reconstruction Project" (北站交通枢纽改造工程) was initiated in response to the growing demand of floor area posed by the increasing passenger traffic after introduction of the high-speed rail service. The station now has an additional 3-storey "Sub-Station Building" (子站房) and a "North Square" (北广场) on the northern (Huanggu District) side of the railways, while the old waiting lounge in the original 16-storey Main Station Building is now relocated to a large elevated concourse that bridges over the rail tracks, with a pillar-less roof (the largest in mainland China) doming the platforms. The original South Square (南广场) outside the Main Station Building was rebuilt into a multi-levelled complex, with two above ground forming an elevated airport-style drop-off zone and a large ground-level area for bus stops, as well as a three-level underground city providing shopping malls, parking lots, taxi pick-up and interchange with Subway Line 2, while also capable of rapid conversion into an air raid shelter if needed.