La Puerta de San Juan is the last of the five gates that allow access into the walled city of Old San Juan. The vibrant red gate, which stands 16 feet tall and dates back to 1635, is located at the end of El Paseo de la Princesa, the historical promenade of San Juan. When the Spaniards moved from Caparra to the islet of San Juan, now known as Old San Juan, they started to build structures to protect the city from attacks and invasions including Fort El Morro, and…