The greater Houston metropolitan area is visible in this low-oblique, northwest-looking photograph. The city is highlighted by an obvious radial pattern of numerous freeways and interstate highways leading into and out of the largest city in Texas. Interstate Highway 45 is the major artery connecting Houston with Galveston Island. The approximate distance from downtown Houston to downtown Galveston is 50 miles (80 kilometers). V-shaped Houston Intercontinental Airport can be seen on the city’s north side. East of the airport is Lake Houston, source of the city’s drinking water. South of Lake Houston, beginning near the downtown area of Houston, is the Houston Ship Channel, which extends to Galveston. Galveston Island is the barrier island southeast of Houston. The city of Galveston can be seen as a grayish area concentrated on the east end of the island. Galveston Bay is shallow—approximately 12 feet (4 meters) deep. The Houston Ship Channel is dredged frequently to facilitate major shipping into Houston, the third largest port in the United States. Texas City, a major site for petrochemical processing, is seen as the highly reflective area on the mainland between the Texas City Dike and the Interstate Highway 45 bridge over the bay to Galveston.