Belvedere Lagoon is an artificial lagoon

Lagoon

A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...

 in the Marin County, California

Marin County, California

Marin County is a county located in the North San Francisco Bay Area of the U.S. state of California, across the Golden Gate Bridge from San Francisco. As of 2010, the population was 252,409. The county seat is San Rafael and the largest employer is the county government. Marin County is well...

 community of Belvedere

Belvedere, California

Belvedere is an affluent city in Marin County, California, United States. Belvedere is located northeast of Sausalito, at an elevation of 36 feet...

 on San Francisco Bay

San Francisco Bay

San Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...

. Narrow strips of land separate it from Richardson Bay

Richardson Bay

Richardson Bay is a shallow, ecologically rich arm of San Francisco Bay, managed under a Joint Powers Agency of four Northern California cities. The Richardson Bay Sanctuary was acquired in the early 1960s by the National Audubon Society. The bay was named for William A...

 (to the northwest) and Raccoon Strait

Raccoon Strait

The Raccoon Strait is a waterway of the San Francisco Bay between Angel Island and the Tiburon Peninsula, mainland Marin County, California.-History:From Angel Island California State Park in San Francisco Bay. Ref. California State Parks Angel Island....

. Rising above the lagoon on higher ground is Ring Mountain

Ring Mountain (California)

Ring Mountain is an elevated landform on the Tiburon Peninsula in Marin County, California. This mountain was named for George E. Ring, who served as a Marin County Supervisor from 1895 to 1903.A number of rare and endangered flora inhabit Ring Mountain...

 on the Tiburon Peninsula. This area of Ring Mountain is notable for its archaeological resources of extant Native American

Indigenous peoples of the Americas

The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...

 petroglyph

Petroglyph

Petroglyphs are pictogram and logogram images created by removing part of a rock surface by incising, picking, carving, and abrading. Outside North America, scholars often use terms such as "carving", "engraving", or other descriptions of the technique to refer to such images...

s as well as a great biodiversity

Biodiversity

Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

 of California native plant

Native plant

Native plant is a term to describe plants endemic or naturalized to a given area in geologic time.This includes plants that have developed, occur naturally, or existed for many years in an area...

s.

The lagoon is owned and maintained by the Belvedere Lagoon Property Owner's Association. The lagoon is not accessible by boat from the San Francisco Bay, and no public access is provided. Until somewhat late in the 20th century houseboats were present in Belvedere Lagoon.