You can’t visit St. Augustine without exploring Florida’s oldest man-made structure of the European era, the Castillo de San Marcos. Welcome to Florida Time, our weekly column about Florida history.

Note: An earlier version of this story stated Castillo de San Marcos is Florida's oldest man-made structure, when really, it's the state's oldest man-made structure of the European era.

Readers: In a state that embodies transience, Castillo de San Marcos -- Florida's oldest man-made structure and America's oldest fort -- wears its age proudly.

Up to a million people a year cross its drawbridge without incident. But over three centuries, raiders have tried, and failed, to take the four-sided fort on Matanzas Bay.

Sir Francis Drake torched the city in 1586, but it wasn't until the British sacked the town again in 1668 that leaders decided their wooden forts were inadequate.

Work started four years later and it took two decades to build the structure, mostly with coquina blocks -- compressed mixtures of oyster shells and lime mined from the adjacent Anastasia Island.

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The incomplete fort survived a 1683 assault and was finished in 1695, in time for a 50-day British siege in 1702 and another attack in 1740. It was renovated in the mid-1700s.

Its angled walls range in thickness from nine to 13 feet. Three sides are surrounded by a moat; the fourth side was filled in for a battery. About 40 cannons ring the fort and you can still see the hot shot oven, where cannonballs were made red hot to set ships afire on impact.

Ironically, nature is slowly doing what raiders could not; sun, sand, sea, waves and wind are eating away at the fort. Officials are studying ways to shore it up.

When the British took Florida in 1763, the bastion was Anglicized as Fort St. Marks. It was a base for raids against rebels in Georgia and South Carolina and a prisoner-of-war stockade.

When Spain regained Florida in 1783, the old name was restored. After Florida became a U.S. possession, it was named Fort Marion. It held Indians in the Seminole wars, was briefly occupied by Confederates in the Civil War and was a military prison in the Spanish-American War.

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The fort became a national monument in 1924 and regained its original name in 1942. It’s just one of several attractions at America’s oldest city.

Fountain of Youth Archaeological Park is another. It’s also one of Florida's oldest tourist attractions. Scholars say there's no evidence Juan Ponce de León ever heard the phrase "Fountain of Youth," much less sought the imaginary place; the legend would spring up (pun intended) more than a decade after Ponce's 1521 death. But go ahead; take a drink. What have you got to lose?

Mission of Nombre de Dios, a reconstructed 1587 mission, stands in front of the 208-foot-tall stainless-steel cross, which signifies the arrival of Christianity in the new world.

Fort Mose State Park, pronounced moh-ZAY, was founded in 1738 as America's first free community of ex-slaves. Archaeologists unearthed it in 1980.

And then there’s Plaza de la Constitución. That slaves were sold somewhere in the city isn't in dispute. Records show some were sold at the open-air structure here at the plaza, now sometimes called the "slave market," but it's unlikely it was formally or regularly used for that purpose. Its main use was sales of produce, meat and fish.

Nearby, the new Foot Soldiers Monument, which honors civil rights pioneers -- the city was Ground Zero for the 1960s civil rights movement in Florida -- overlooks a bank that once was a Woolworth's department store where desegregation sit-ins occurred. Down the street is the site of Monson Motor Lodge, torn down years ago. In June 1964, Martin Luther King Jr., and other blacks were refused service at the motel's restaurant, and some blacks defiantly jumped in its pool. The owner poured pool acid to run them out, and the image, shown nationwide, helped push through the 1964 Civil Rights Act.

St. Augustine Visitor Center: 904-825-1000. www.historicstaugustine.com.


Next week: The first theme park

Last week: The tacky side of Florida’s past, bloopers and buffoons included

From a reader: A hearty thank you, Mr. Kleinberg, for your articles on Florida history. I've lived in Florida since the early 70s and had no inkling about the fascinating information you include. Please don't stop educating us! Jo, Sarasota
