Downtown is the largest central business district in the city of Houston and the largest in the state of Texas, located near the geographic center of the metropolitan area at the confluence of Interstate 10, Interstate 45, and Interstate 69. The 1.84-square-mile (4.8 km2) district, enclosed by the aforementioned highways, contains the original townsite of Houston at the confluence of Buffalo Bayou and White Oak Bayou, a point known as Allen's Landing. Downtown has been the city's preeminent commercial district since its founding in 1836.

Buffalo Bayou is a slow-moving body of water which flows through Houston in Harris County, Texas. Formed 18,000 years ago, it has its source in the prairie surrounding Katy, Fort Bend County, and flows approximately 53 miles (85 km) east through the Houston Ship Channel into Galveston Bay and the Gulf of Mexico. In addition to drainage water impounded and released by the Addicks and Barker reservoirs, the bayou is fed by natural springs, surface runoff, and several significant tributary bayous, including White Oak Bayou, Greens Bayou, and Brays Bayou. Additionally, Buffalo Bayou is considered a tidal river downstream of a point 440 yards (400 m) west of the Shepherd Drive bridge in west-central Houston.