considered to be his finest, was innovative in that the building is built around an interior courtyard, thus allowing natural light and fresh air to reach most of the building. The courtyard is surrounded by four stories in three sides. A tower rises five stories from the courtyard's open side. As was usually the case with Richardson's buildings, the roof is steep with dormers placed at all the corners. A prison is connected to the courthouse via the "Bridge of Sighs". The design was based on the Bridge of Sighs in Venice. The entire complex was built of large rusticated blocks of granite, with the entrance ways and windows topped with wide arches. This gives the building a heavy, stable and dignified appearance. In the 1900s the street level in front of the building was lowered as part of a general re-grading of Pittsburgh. Richardson had anticipated this and courses of finished masonry had been buried underground, now to be revealed. Unfortunately this left the ceremonial entrance a full story above the street. A grand stairway was built, but removed during street widening in the 1930s- the low arched doorways were extended downwards to street level, with the result that the visitor is not greeted by the grand entrance hall Richardson planned, but by the low corridors which were once the basement. Muralist Vincent Nesbert completed five murals for the building on its first floor in 1937: "Industry," "Justice," "Peace," "Fort Duquesne" and "The Battle of Grant's Hill." In 1973, the building was placed on the National Register of Historic Places. In 1976, it was designated a National Historic Landmark. Legacy and impact The design of the Allegheny County Courthouse has influenced buildings in many cities across North America, such as Toronto City Hall, Minneapolis City Hall, the Milwaukee Federal Building, Altgeld Hall on the campus of the University of Illinois at Urbana–Champaign and James W. McLaughlin's Wayne County Courthouse in Richmond, Indiana. In 2007, the American Institute of Architects asked Harris Interactive to survey 2,000 people, who were shown 247 photographs of buildings and other structures in different categories chosen by 2,500 architects. The Allegheny County Courthouse was ranked 35th overall on the list and above every other courthouse in the nation except the United States Supreme Court Building. In popular culture Several big-budget films have portrayed the Courthouse. Striking Distance and Hoffa primarily used interior shots, while Desperate