Located on the west bank of the modern Panama Canal, Fort San Lorenzo is an outstanding example of Spanish Colonial military architecture. Construction of the structure was started in 1595 upon the orders of King Philip the Second of Spain to protect the mouth of the Chagres River, a strategic waterway connecting the Atlantic and Pacific oceans. Control of the waterway provided access to the riches of the South American colonies along the Pacific Ocean and the site was considered to be one of the 'keys' to the Americas. Due to its strategic location the fort was under constant attack by pirates and other conquering forces and as a result, the fort had to be rebuilt three times between the 17th and 18th centuries.