Venture into the tunnels and dungeons of the largest fort Spain ever built in the Americas. Located close to the eastern entrance to Old San Juan, it was built to guard against land attacks. The views of the Atlantic are breathtaking, and the tour guides are extremely knowledgeable and friendly. A folkloric group performs every Monday. June-November daily 9 am-5 pm; December-May daily 9 am-6 pm. US$3 adults, free for children younger than 16. US$5 adults for combined entrance to the Castillo de San Cristobal and Castillo de San Felipe del Morro. Calle Norzagaray (at the eastern end of the street), Old San Juan, San Juan. Phone 787-729-6960. http://www.nps.gov/saju.
