Outside of the urban centers, older regions of San Diego County south of the San Diego River, as well as La Jolla and Pacific Beach, are built on a street grid. Suburban growth north of the San Diego river were built as master planned suburban communities on top of mesas with the "city of villages" concept in mind, built around car-dependency. Tijuana's suburban landscape is made up densely packed low-density mixed land uses, with patches of street grids east of the city and more organic growth influenced by topography. Cities like Tecate and Rosarito are built on street grid systems.