falling and rents were rising. Even HRPT Properties Trust had leased 70 percent of the space Comcast vacated by 2007. The predictions by opponents did not occur mainly because Comcast ended up leasing 89 percent of the building and the offices for the Comcast Center's second-largest tenant, Citizens Bank of Pennsylvania, were new to the city. Building Comcast Center has 58 floors, of which 56 are occupiable. The structure of the Comcast Center comprises a central concrete core with steel-framed floors. The building's exterior features a glass curtain wall made of lightly tinted, non-reflective low-emissivity glass. The tower tapers inward towards the top and features two cutouts near the top of the building on the north and south sides. To prevent the tower from swaying too much in the wind, the Comcast Center contains a double-chambered concrete tuned liquid column damper, the largest such damper in North America. Receiving a gold Leadership in Energy and Environmental Design (LEED) rating in April 2009, the Comcast Center is the tallest LEED building in Philadelphia. The building was designed to use 40 percent less water than a typical office building, and the plaza was designed to reduce heat-island effect from the pavement by 70 percent. Reducing air conditioning and lighting costs, the low-emissivity glass curtain wall blocks 60 percent of heat while allowing 70 percent of the Sun's light inside. The skyscraper has of rentable space, including of restaurant and retail space called The Market at the Comcast Center. of retail space is on the underground concourse while the rest is located on the street level. The building features high ceilings with some floors having a ceiling height of . The lower floors on the south side of the building feature four three-story stacked atrias. The building also features a 500-seat concourse level dining court and an 87-space private underground parking garage. ThyssenKrupp provided the building's 30 gearless elevators, seven hydraulic elevators, and two escalators. The Comcast Center faces a half-acre public plaza. The plaza, designed by Lucinda Sanders of OLIN, sits over underground railroad tracks. It features a seasonal outdoor restaurant, Plaza Cafe at Table 31, that is sheltered by a trellis. Between the cafe and the building entrance is a choreographed fountain designed by Wet. The tower's entrance is a tall winter garden. The winter garden entrance directly connects to the underground concourse of Suburban Station. The building also has a