The display is made from about 550 Nokia Phones. (The good people over at WPCentral actually counted them.) The event took place in front of the soon to be opened Nokia Flagship store and featured demo phones that people could try out and leave with informational pamphlets. The event also had several sections such as one that featured gaming, one for the Windows Phone, and one for general promotion.
Source: We Love WP HK via WPCentral