The tiny, 1742-built Fort Matanzas National Monument is located on Rattlesnake Island, near where Menéndez de Avilés executed hundreds of shipwrecked French soldiers and colonists when rations at St Augustine ran low. Today it makes a terrific excursion via a free 10-minute ferry that launches every hour (at half-past) from 9:30am to 4:30pm, weather permitting. Once there, the ranger provides an overview and lets you wander.
From Daytona, take I-95 north to exit 289. Exit right and follow Palm Coast Pkwy (a toll road) until you reach Hwy A1A. Turn left and follow A1A north to the monument, which will be on your left. The trip should take just under one hour.
To catch the 35-person ferry to the monument – the last free thing in Florida – go through the visitor center and out to the pier.