<P> The `` East Bay '' is the densest region of the Bay Area outside of San Francisco and includes cities and towns in Alameda and Contra Costa counties , centered around Oakland . As one of the larger subregions , the East Bay includes a variety of enclaves , including the suburban Tri-Valley area and the highly urban western part of the subregion that runs alongside the bay . The `` Peninsula '' subregion includes the cities and towns on the San Francisco Peninsula , excluding the titular city of San Francisco . Its eastern half , which runs alongside the Bay , is highly populated while its less populated western coast traces the coastline of the Pacific Ocean and is known for its open space and hiking trails . Roughly coinciding with the borders of San Mateo county , it also includes the northwestern Santa Clara county cities of Palo Alto , Mountain View , and Los Altos . The `` South Bay '' includes all of the rest of the cities in Santa Clara county , centered around San Jose , the largest city in Northern California . It is roughly synonymous with Silicon Valley due to its high concentration of tech companies , although the industry also has a significant presence in the rest of the Bay Area . The `` North Bay '' includes Marin , Sonoma , Napa , and Solano counties , and is the largest and least populated subregion . The western counties of Marin and Sonoma are encased by the Pacific Ocean on the west and the bay on the east , and are characterized by its mountainous and woody terrain . Sonoma and Napa counties are known internationally for their grape vineyards and wineries , and Solano county to the east , centered around Vallejo , is the fastest growing region in the Bay Area . </P>
<P> The `` East Bay '' is the densest region of the Bay Area outside of San Francisco and includes cities and towns in Alameda and Contra Costa counties , centered around Oakland . As one of the larger subregions , the East Bay includes a variety of enclaves , including the suburban Tri-Valley area and the highly urban western part of the subregion that runs alongside the bay . The `` Peninsula '' subregion includes the cities and towns on the San Francisco Peninsula , excluding the titular city of San Francisco . Its eastern half , which runs alongside the Bay , is highly populated while its less populated western coast traces the coastline of the Pacific Ocean and is known for its open space and hiking trails . Roughly coinciding with the borders of San Mateo county , it also includes the northwestern Santa Clara county cities of Palo Alto , Mountain View , and Los Altos . The `` South Bay '' includes all of the rest of the cities in Santa Clara county , centered around San Jose , the largest city in Northern California . It is roughly synonymous with Silicon Valley due to its high concentration of tech companies , although the industry also has a significant presence in the rest of the Bay Area . The `` North Bay '' includes Marin , Sonoma , Napa , and Solano counties , and is the largest and least populated subregion . The western counties of Marin and Sonoma are encased by the Pacific Ocean on the west and the bay on the east , and are characterized by its mountainous and woody terrain . Sonoma and Napa counties are known internationally for their grape vineyards and wineries , and Solano county to the east , centered around Vallejo , is the fastest growing region in the Bay Area . </P>
what part of the bay area is san jose
what part of the bay area is san jose
South Bay
South Bay