Marincello, Natural landscape in Marin Headlands, US.

Marincello is a name given to the Marin Headlands land where a 2,138-acre planned community was proposed and never built. The site lies in a coastal valley of rolling green and brown hills, with a cluster of red-roofed, white-walled buildings and a paved parking lot near a sandy beach and lagoon; a rocky headland and small offshore island close the view.

In 1965 Marin County approved Thomas Frouge's plan for Marincello, a community of 20,000–30,000 people in 50 apartment towers, funded with Gulf Oil. Construction stalled in 1967 amid lawsuits over zoning and access. After Gulf Oil lost a key case in 1970, it sold the land to The Nature Conservancy, which transferred it to the National Park Service two years later.

The name Marincello was coined by developer Thomas Frouge as a contraction of "Marin" and "Monticello", echoing Thomas Jefferson's Virginia estate. The planned city was never built, and the name now survives only on the Marincello Trail, the dirt route that follows the course of the five-lane boulevard bulldozed up the hillside in the 1960s.

The main trail follows the old planned roads and offers easy walking with coastal views. Bring sturdy shoes and be ready for changing weather conditions.

Abandoned entrance gates and graded roads scattered through the land remain as physical traces of the failed 1960s development plan. These remnants show how close the area came to being transformed completely.