Paseo del Morro is a boardwalk that borders the outer edge of Old San Juan's imposing Castillo San Felipe del Morro. One one side, you'll be flanked by the fort's massive outer walls and on the other side, you'll walk next to the Bay of San Juan. Once you reach the famous Gate of San Juan, a giant doorway that gives access to the inside of the city walls, the Paseo del Morro becomes one with the Paseo de la Princesa.