On the grounds in front of Castillo San Felipe del Morro hundreds of Dutch and Spanish soldiers were killed in 1625. In a month-long attack and siege, Dutch forces tried to take San Juan, and almost succeeded. Eventually Spanish defenders in El Morro, along with many townspeople drove them away. As they left, the attackers looted and burned the city.
The attack showed Spain that even stronger defences were needed to hold San Juan, and it confirmed the loyalty of the local people, who fiercely fought for Spain. Today a monument commemorating those who fought and lost their lives in the battle stands by the path to the castle.
- Information sign at Castillo San Felipe del Morro