The term Downtown Indianapolis refers to the central business district of Indianapolis, Indiana, USA. The boundaries of downtown Indianapolis have varied over time as the city has grown. The city's original platted area, the Mile Square, (bounded by North, South, East, and West streets) is sometimes used to denote the downtown area. However, the Indianapolis Regional Center Plan, which is the official plan for Downtown Indianapolis, defines the boundaries to be 16th Street on the north, Interstate 65/70 on the east, Interstate 70 on the south and the Belt Railroad on the west.