The largest and most impressive of Puerto Rico's capital is the enormous, imposing Castillo San Felipe del Morro, the fortress occupying the city's northeastern tip, constructed in the mid-16th century and enlarged over the ensuing years. Right nearby is a second, even larger fortress (the largest Spain ever built in the Americas, in fact), the nearby 17th-century San Cristóbal, and both are flanked by a doughty wall nearly four kilometres (2½ miles) long and 13 metres (nearly 43 feet) high. The third, called simply La Fortaleza (The Fortress), was San Juan's first defensive fortification, dating to its very earliest years, which has ever since then also served as the residence of Puerto Rico’s governor – making it the world's oldest executive mansion in continuous use. All of these are part of the city's UNESCO World Heritage Site. 

Read more about this and other San Juan sights in my post Marking its 500th Anniversary, Old San Juan Is an Atmospheric Classic.

KeriWiedemann