In central London, the opportunity to build above rail lines near Liverpool Street Station spurred the construction of Broadgate, a new business district. SOM devised the master plan, and over three decades, designed several of the site's 14 buildings. In order to build high-rise structures atop one of the city's busiest stations and its railyard, SOM's structural engineering team devised a deck over the tracks to allow for various building configurations on top. Exchange House, completed in 1990, is a building that acts as a bridge spanning the tracks. In 2008, Broadgate Tower, the district's tallest building, was completed. SOM also designed public space enhancements for the area.