Approaching from the west, Portobelo's first fort is Fuerte Santiago. Built in 1753, some 14 years after Vernon’s attack, some walls were 3m thick and made of cut coral blocks. Known to the Spaniards as ‘reef rock,’ coral was a popular building material since it’s easily shaped, tough as granite yet light as pumice. Ruins include officers’ quarters, artillery sheds, a sentry box, barracks, watchtowers and a half-dozen cannons.
Following mudslides, some coral walls had to be replaced with concrete reinforcements. Spot them to the right as you go through the main entrance.