A new bridge installed this week in downtown Phoenix physically fused the Phoenix Convention Center's newest additions: the already-open West Building and the soon-to-be-completed North Building. Its installation is a major milestone in a $600 million expansion project that will make the convention center one of the 20 largest facilities of its kind in the nation, according to a center release.The bridge which is 150 feet long and weighs 82.5 tons was hauled through the streets of downtown Phoenix in the early-morning hours of Jan. 22, then hoisted into place 54 feet above Third Street. The steel structure eventually will be encased in glass, providing its users with views of Phoenix's urban landscape and the ridgeline of nearby South Mountain.The sky bridge connects the uppermost levels of the West Building, with a 46,000-square-foot ballroom, and North building, with 190,000 square feet of virtually column-free exhibition space and outdoor meeting areas.The North Building, which is three times the size of the West Building, occupies an entire city block. When complete, it will feature amenities such as a street-level ballroom, 56 meeting rooms, and a food court with five themed eateries and outdoor seating, according to the release.The sky bridge will be just one of the crossings between the neighboring buildings. In addition to pedestrian crossing on the street level, convention-goers will be able to flow from one building to the other via a shared underground exhibition hall the size of six football fields. This sub street gallery will feature 32-foot ceilings and floors scored in 10-by-10-foot squares for easy booth setup.When it welcomes its first meeting groups in January 2009, the fully expanded Phoenix Convention Center will feature nearly 900,000 square feet of exhibition and meeting space, three ballrooms with cutting-edge audio and video technology, $3.2 million worth of public art, and ecologically friendly features like solar paneling and a water-harvesting garden. The convention center also will be a major stop on the METRO Light Rail line, which will link downtown to Phoenix Sky Harbor International Airport and the neighboring cities of Tempe and Mesa.