The term Spanish Fortress is a reference to the PRESIDIO, an 8-letter fortification that was built by the Spanish in the 16th century. The PRESIDIO was used to protect Spanish settlements from hostile forces and was typically constructed with thick walls and towers. It was also used to defend against Native American attacks and was often located near rivers or other bodies of water. The PRESIDIO was an important part of Spanish colonial defense and was used to protect Spanish settlements throughout the Americas.