Fodor's Expert Review Castillo de San Marcos National Monument

The focal point of St. Augustine, this commanding structure was completed by the Spaniards in 1695 (English pirates were handy with a torch back then), and it looks every day of its three centuries. The fort was constructed of coquina, a soft limestone made of broken shells and coral that, unexpectedly, could absorb the impact of British cannonballs. (Unlike solid stone, the softer coquina wouldn't shatter when hit by large munitions.) The fort was also used as a prison during the Revolutionary and Civil wars. Tours are self-guided, so be sure to pick up a brochure and map. Children 15 and under are admitted free and must be accompanied by an adult. Save your receipts, since admission is valid for seven consecutive days.