Remote Florida Keys Outpost

Dry Tortugas: A Massive Brick Fortress in the Middle of the Sea

Key West, Florida, United States

By the Wicked Cool Places editors · Published Wed, Mar 18, 2026 · Updated Tue, Jul 21, 2026

Why it’s cool

This isolated archipelago features a colossal, unfinished hexagonal fortress built from 16 million bricks and surrounded by a "ship trap" graveyard of 17th-century wrecks.

Southeast Adventure

Seventy miles past the end of the Florida Keys, where the Atlantic meets the Gulf of Mexico, sits a massive hexagonal anomaly rising from the turquoise water. This is the Dry Tortugas, a cluster of coral islands first charted by Juan Ponce de Leon in .

Originally named for the abundance of sea turtles that provided sustenance for early explorers, the "Dry" prefix was later added as a grim warning to sailors that these islands held no natural source of fresh water. Today, the site remains one of the most secluded and hauntingly beautiful outposts in the American National Park system.

Why It Stands Out

The defining feature of the islands is Fort Jefferson, a staggering architectural feat that utilized over million bricks. Construction began in to secure the Gulf Coast against piracy, but the project spanned thirty years and was never truly finished.

Despite its incomplete state, the fort is one of the largest masonry structures in the world, featuring a -foot-wide moat and walls designed to house hundreds of heavy guns. Beyond the brickwork, the surrounding waters earned a reputation as a "ship trap" due to treacherous weather and seasonal shallows.

The seafloor here is a maritime graveyard, preserving th-century vessel remains, antique glassware, and rusted cannons. Such deep-sea mysteries are also a focus of the International Cryptozoology Museum.

The fort also served a darker purpose as a Civil War-era prison. Its most notable resident was Dr.

Samuel Mudd, the physician who treated John Wilkes Booth after the assassination of Abraham Lincoln. Mudd was eventually pardoned after he heroically stepped in to treat a yellow fever outbreak that killed the fort's primary doctor.

Before You Go

Reaching this remote destination requires a seaplane or a ferry from Key West. While the boat ride is scenic, the seaplane offers a unique vantage point to spot sea turtles and sharks in the clear water below.

The environment is rugged; the sand can become extremely hot, and the historic masonry of the fort includes uneven stone surfaces, so sturdy closed-toe footwear is essential. Visitors are generally free to explore most of the grounds, provided they steer clear of active preservation zones.

Questions worth answering

How do we actually get to a fortress seventy miles out at sea?

You'll need to book a ferry or a seaplane from Key West. We suggest the plane if you want to spot sharks and sea turtles from above before landing.

Is the fort just a pile of old bricks?

It's a hexagonal structure made of 16 million bricks that served as a Civil War prison for Dr. Samuel Mudd. The site also overlooks a maritime graveyard of 17th-century shipwrecks and rusted cannons.

What should we wear for a day on the islands?

Don't show up in flip-flops. The sand gets incredibly hot and the fort's masonry is full of uneven stone and potential hazards, so you'll want sturdy closed-toe shoes.

Where did the original research for this guide come from?

The initial data came from Dry Tortugas, and we took our own editorial from there to highlight the site's history as a waterless outpost and massive masonry feat.

Visit Snapshot

Access is restricted to boat or seaplane travel from Key West. Seaplane passengers often get the best views of marine life from above.

Wear durable shoes rather than flip-flops, as the fort contains stone hazards and the sand can reach high temperatures. Most areas of the fort are open for self-guided exploration except for sections currently undergoing restoration.

Location

Key West, Florida

Know before you go

The best way to get there is by sea plane from Key West. When flying, you will be able to look down and see large sea turtles and other sea creatures.

When visiting, I recommend adequate footwear because the sand is hot and the fortress is littered with stone and other hazards. It's a pretty free range place; we felt free to walk wherever wasn't under rehabilitation.

Editorial source

Dry Tortugas

Juan Ponce de Leon first stumbled upon this stretch of islands in , back when they were nothing more than clusters of coral inhabited by sea turtles. Upon his discovery, de Leon named the islands "Las Tortugas" (meaning "the turtles"), and is said to have subsisted off of these very animals while on his journey through the high seas.

("Dry" was later added to the islands' name as an attempt to warn mariners of the lack of freshwater in the area.) After de Leon's discovery, the Dry Tortugas became a fixture on Spanish ship maps for merchants and explorers going to and from the Gulf Coast. Seventy miles west of the Florida Keys, and in a prime location between the Gulf of Mexico and the Atlantic Ocean, the Dry Tortugas soon became a popular shipping corridor.

Despite the passageway's popularity, the Dry Tortugas also became the site of hundreds of shipwrecks. The seasonal shallow waters and hazardous weather conditions lent to the corridor's infamous title as the "ship trap." To this day, a large collection of sunken treasures still lies beneath the surface waters.

Seventeenth-century vessel remains, cannons, and glassware are among some of the maritime relics. Of all the Dry Tortugas treasures, though, Fort Jefferson perhaps remains the crown jewel.

Once Florida was acquisitioned from Spain in , the United States began plans to erect a naval station that would help combat piracy in the Caribbean. Eventually, the U.S.

Navy agreed on the Dry Tortugas as the site for their fortress, arguing that U.S. shipping in the Gulf Coast would be in jeopardy if a hostile power were to take over the islands. In , after seventeen years of extensive planning, Fort Jefferson began construction on the Garden Key Island.

The design plans called for a practically indestructible hexagonal fortress, complete with a massive heavy-gun platform. Two sides of the fort measured feet and four sides measured feet.

The structure stood -feet above sea level, surrounded entirely by a wall and a -foot wide moat. Though construction lasted for roughly thirty years, Fort Jefferson was never fully completed.

Despite this, million bricks were laid, making it one of the largest coastal forts ever built. During the Civil War the fort was also used as a prison, mainly for Union deserters.

The most famous inmate, however, was Dr. Samuel Mudd, who was convicted of conspiracy in the assassination of President Abraham Lincoln.

After shooting President Lincoln, John Wilkes Booth jumped from the theater box, broke one of his legs, and immediately fled to Dr. Mudd's farm where he received medical assistance.

In , Dr. Mudd was sentenced to life in prison and sent to the remote fortress.

Two years later, a yellow fever outbreak occurred at Fort Jefferson. The outbreak took a number of lives, including the lone doctor who had been stationed at the fort.

Dr. Mudd agreed to step in as a replacement and, as a result, many lives were saved.

Consequently, the soldiers started a petition demanding Dr. Mudd's release; a petition which President Andrew Johnson granted only four years into Dr.

Mudd's life sentence. The fort was abandoned by the Army in .

In later years it served as a coaling station, a quarantine station for the Marine-Hospital Service from -, during which the location was also used in the Spanish-American War and, in , it was registered by President Roosevelt as a National Monument. Today it operates as part of the Dry Tortugas National Park.

Accessible only by boat or seaplane, the Dry Tortugas are considered to be one of America's most remote and least visited national parks.

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