The Houston and Galveston metropolitan areas are apparent in this southeast-looking, low-oblique photograph. Houston, the fourth most populous city in the United States, is one of the world’s major oil centers; a great commercial, financial, medical, and industrial hub; and home of the NASA Lyndon B. Johnson Space Center. Access to the Port of Houston, the third-busiest port in the United States, is possible via a dredged channel from the Gulf of Mexico through shallow Galveston Bay. Galveston has major shipbuilding and repair yards and is a major tourist area. Rich agricultural lands of the coastal plain surround Houston from the south to the northwest. The large smoke plume (left center) was caused by an explosion and fire at a major oil refinery in the small community of Mont Belvieu.