The Art Institute building is unusual because it is two sets of buildings linked by a two-story bridge over open-air railroad tracks. The construction of Millenium Park moved the Metra Electric and South Shore railroad lines underground. This made room for the new Modern Wing and exterior courtyards. Before this change, the lower level of the bridge building was formerly the windowless Gunsaulus hall, but is now home to the Alsdorf Galleries showcasing Indian, Southeast Asian and Himalayan Art. The renovation added windows facing north toward Millennium Park. Renzo Piano designed the gallery space in conjunction with his design of the Modern Wing. The gallery features the same window screening used there to protect the art from direct sunlight. The upper level of the bridge building formerly held the modern European galleries, But it was renovated in 2008. The galleries now show Impressionist and Post-Impressionist art.