Starting out as a single tower in the 16th century to the impenetrable fortress known today, Castle San Felipe del Morro has a long and intriguing history. The fort was built as an alternative to La Fortaleza (the governor's residence), the only defense for the city at the time, due to its location being too inland, giving the enemy easy access into San Juan.
The design of the fortress is said to be inspired by the shape of a goat's head, a design that can be found decorating the entrance to fort's chapel though the claims are still debated.
Contrary to popular belief, the biggest contributors to El Morro's design and construction were not the Spaniards but foreigners employed by the crown, these being: Battista Antonelli (16th century), a renowned Italian architect under the Hapsburg banner, who was in charge of designing the fort's current appearance; and Irishmen Alexander O'Reilly and Thomas O'Daly (late 18th century), who updated El Morro by improving its stonework and building cisterns under the plaza.
The fortification took around 200 years to be fully built and throughout its centuries of activity it only suffered two known defeats, one at the hands of the British in 1598 and the other by Americans during the Spanish-American War in 1898, leading to the end of Spanish rule on the island.