SOM designed the master plan for Chicago's Millennium Park, which opened in 2004 and has become one of the city's most visited attractions. Constructed above bus lanes, parking garages, and a rail yard, Millennium Park can be considered the world's largest roof garden. Below the great lawn, two new levels of parking were built, bus stops were added, and rail stations were renovated and expanded, including Millennium Station. The project revitalized a formerly blighted downtown site and marked the completion of Chicago planner Daniel Burnham’s 100-year vision for the area.