Presidio is a term that refers to a fortified military base or STRONGHOLD. It is derived from the Spanish word presidio, meaning 'FORT'. The term is commonly used to refer to a fortification built by the Spanish in the Americas during the colonial period. In the United States, the term is also used to refer to a type of military base, such as the Presidio of San Francisco, which was established in 1776. The term can also be used to refer to a fortification built by other nations, such as the British in India. The term Presidio is also used to describe a type of fortification that is smaller than a fortress, but larger than a castle.