Fort San Geronimo is a historic military fort located in San Juan, Puerto Rico. Built in the late 18th century, it was designed to protect the city from naval attacks and invasions. The fort features a unique blend of Spanish colonial architecture and military design, showcasing the strategic importance of the area during its time. Today, Fort San Geronimo is a popular tourist attraction, offering visitors a glimpse into Puerto Rico's colonial past. The site is part of the larger San Juan National Historic Site, which includes other significant structures like El Morro and San Cristóbal.