The Los Angeles Westside is an urban region in the western Los Angeles County portion of California in the United Sates. It is comprised of 101.28 square miles (262 km2), encompassing 28 districts in the city of Los Angeles including Venice, Mar Vista, Brentwood, Westwood, Pacific Palisades, West L.A., Rancho Park-Cheviot Hills, Century City, Playa Vista, Beverlywood, Westchester, Playa Del Rey and unincorporated Marina Del Rey, plus the cities of Beverly Hills, Culver City, Santa Monica and West Hollywood. The term "Westside" is often used interchangeably with "West L.A." by Los Angeles residents, with La Brea Avenue being the commonly accepted eastern borderline and the Pacific Ocean being the western borderline. The Westside is one of the most important economic, commercial, and cultural centers in the United States as well as being home to some of the most affluent residential neighborhoods in the world.