A single line of clouds and shadows obscure some of the landscape from the central business district of Houston to Texas City to the southeast. Many linear features are highways, including Interstate Highway 45 (the Gulf Freeway) and surrounding highways; railroad rights-of-way; or combinations of a highway and a railroad in close proximity. The highly reflective features indicate large industrial plants (oil refineries and chemical plants) and commercial sites (strip shopping centers and malls). Large concentrations of manufacturing plants line the Houston Ship Channel and surround Texas City. The Lyndon B. Johnson Space Center sits on the north shore of Clear Lake. The single line of islands at the convergence of the San Jacinto River and the northwest corner of Galveston Bay was created by the dredged materials from the Houston Ship Channel. Rural areas outside the urban area are used for pastures or agricultural fields.