Lima geography is dominated by its location. Stretched on a mostly flat terrain in the Peruvian coastal plain, caught between the Pacific Ocean and the beginning slopes of the Andes, already rising to 500 meter above sea level within the city boundaries, Lima nevertheless is a desert city. Being the second biggest desert city in the world, after Cairo Egypt, apart from the typical plains within Lima geography exist isolated hills which are not connected to the surrounding hill chains of the beginning Andes. The San Cristobal hill, one of the most outstanding in the Lima geography, located in the Rimac district, which faces directly north of the downtown area, is the local extreme of an Andean hill outgrowth. Metropolitan Lima has an area of 2,672.28 km2. The urban area extends around 60 km from north to south and around 30 km from west to east. The city center is located 15 km inland at the shore of the Rimac river. While no official administrative definition for the city exists, it is usually considered to be composed of the central 30 out of the 43 districts of Lima Province, corresponding to an urban area centered around the historic Cercado de Lima district.