The metropolitan region is situated along the Pacific Coast, on the border between the United States and Mexico. The region lies just south of Orange County and west of Imperial County, and shares borders with Greater Los Angeles. The area has a varied topography with over seventy miles of coastline and snow-capped mountains that rise to the northeast, in San Diego County. The terrain includes flood plains, canyons, steep hills, and mesas. The region has its eastern terminus in the Colorado Desert and Imperial Valley regions, where another conurbation – Mexicali–Calexico – is formed. The urbanized area where San Diego and Tijuana meet is known as San Ysidro on the American side of the border and Colonia Federal/Colonia Libertad on the Mexican side. East from the coast , the Tijuanense boroughs of Mesa de Otay and Centenario are heavy urbanized whereas the corresponding American area of Otay Mesa is composed of primarily dispersed industrial and distribution facilities. At the Pacific Ocean region of the border, the border is urbanized on the Mexican side while the adjacent American side is an estuarine preserve, and thus not urbanized.