south side of the building, sloping upward toward Franklin Street to the east. The Franklin Street side of the building was lower than the Wacker Drive entrance, so the entrances on Franklin Street were actually below the plaza, leading to the building's lower mezzanine. Below ground level are three basement levels with a total area of . The basements included a 1,200-seat cafeteria, commercial space, service areas, and a loading dock for 17 trucks. The basement also contained a 150-spot parking garage. , the building's base covers and contains two lobbies for tenants. The building's tenants primarily enter from Wacker Drive and Franklin Street. Shoppers, restaurant patrons, and visitors to the Skydeck observation deck use the southern entrance on Jackson Boulevard. The Wacker Drive lobby contains In the Heart of this Infinite Particle of Galactic Dust, a 2019 artwork by Jacob Hashimoto. It consists of over 7,000 rice-paper and resin disks that are hung from the ceiling. To honor Khan's contributions to skyscraper engineering design, the Structural Engineers Association of Illinois also commissioned a sculpture of him for the lobby of the Willis Tower. The commercial complex at the building's lowest stories is known as the Catalog, a reference to Sears' mail-order catalogs. The six-story complex includes numerous restaurants. It extends into three of the building's basement levels, as well as the three-story annex to the south and west of the tower. The roof of the annex includes a curved skylight with 240 glass panes, and the northern section of the annex's roof is supported by black columns that resemble those in the original tower. The Catalog also contains decorative details, such as handrails and staircase landings, which are inspired by elements of Chicago's "built environment". The third story of the Catalog contains a 30,000-square-foot coworking space operated by Convene. Skydeck The Willis Tower observation deck, called the Skydeck, opened on June 22, 1974. Located on the 103rd floor, above ground level, it is the highest observation deck in the United States and one of Chicago's most famous tourist attractions. Tourists can experience how the building sways in wind and see far over the plains of Illinois and across Lake Michigan to Indiana, Michigan, and Wisconsin in clear conditions. Elevators reach the top in about 60 seconds, allowing occupants to feel the change in pressure as they ascend. The Skydeck competes with the John Hancock Center's observation floor a mile