Sea forts were strategic bases usually built on small islands or shallows that lies at a significant distance from the shore. A sea fort was exactly as the name indicates - a giant fort with stone walls and housing cannons to fend off intruders. Today, the sea forts are mostly deserted, but some of them have been renovated and converted into tourist attractions. 1. Red Sands Fort, UK link The seven towers of Red Sands were placed approximately six miles off Minster, Isle of Sheppey in the Thames Estuary, over the period July 23rd to September 3rd 1943. The forts were designed to house various gun installations to combat the twin threats of enemy aircraft and E-boats (fast warships). link The forts were not a popular posting and were abandoned wholesale by the military at the end of the war after which ownership became a matter of opinion as they were generally considered to be situated in international waters and not subject to any particular mainland jurisdiction. [link, map] 2. No Man's Land Fort, UK link No Man's Land Fort was a fort built in the Solent as part of the Palmerston Forts. It is 2.2 km (1.37 mi) off the coast of the Isle of Wight and built between the years 1867 and 1880 to protect Portsmouth. It was built for a cost of £462,500, which if adjusted for inflation is equivalent to £43,391,356 ($67,783,806) at 2010 prices. link No Man's Land Fort has been used as a luxury home/hospitality centre for high-paying guests - due to the privacy it offers - with an indoor swimming pool and two helipads. In July 2004, Legionella bacteria found in the hotel's water system forced its closure. The Fort was put up for sale in 2005 and again in 2007, but the company collapsed. [link, map] 3. Fort Jefferson, Florida, USA link Fort Jefferson is an unincorporated community and abandoned sea fort in Monroe County, Florida, United States. It is located on Garden Key in the lower Florida Keys within the Dry Tortugas National Park, about 70 miles (110 km) west of the island of Key West. Fort Jefferson is a massive but unfinished fortress. It is the largest masonry structure in the Western Hemisphere, and is composed of over 16 million bricks. Construction began in 1846 and lasted for 30 years. link Fort Jefferson was built to protect one of the most strategic deepwater anchorages in North America. By fortifying this spacious harbor, the United States maintained an important “advance post” for ships patrolling the Gulf of Mexico and the Straits of Florida. [link1, link2, map] 4. HM Fort Roughs (Principality of Sealand), UK link HM Fort Roughs was one of several World War II installations that were designed by Guy Maunsell and known collectively as Maunsell Sea Forts, and its purpose was to guard the port of Harwich, Essex. The naval fort is situated on Rough Sands, a sandbar located approximately six miles from the coast of Suffolk and eight miles from the coast of Essex. It is today the self-proclaimed and unrecognised state, the Principality of Sealand. link Fort Roughs was constructed in 1942. It comprised a floating pontoon base with a superstructure of two hollow towers joined by a deck upon which other structures could be added. The pontoon was reinforced concrete measuring 168 by 88 feet (51 by 27 m). The fort was topped by a gun deck, an upper deck and a central tower unit which housed the radar equipment. The twin towers were divided into seven floors that provided dining and sleeping accommodation and storage areas for generators and munitions. [link, map] 5. Murud-Janjira, India link Murud-Janjira is the local name for a fort situated in the Raigad district of Maharashtra, India. It was occupied by the Siddis and is famous for being the only fort along India's Western coast that remained undefeated despite Dutch, Maratha and English East India Company attacks. link Murud-Janjira Fort is situated on an oval-shaped rock off the Arabian Sea coast near the port town of Murud, 165 km (103 mi) south of Mumbai. Janjira is considered one of the strongest marine forts in India. The fort is approached by sailboats from Rajapuri jetty. The main gate of the fort faces Rajapuri on the shore and can be seen only when one is quite close to it. It has a small postern gate towards the open sea for escape. [link, map] 6. Fort Pampus, Netherlands link Pampus is an artificial island and fort located in the IJmeer near Amsterdam. It was completed in 1895 as part of the Defence Line of Amsterdam. In 1996 it was designated a UNESCO World Heritage Site as part of the Defence Line. link In 2007, the fortress was partially restored. It is open to the public from April to October. It can be reached by a ferry from Muiden or by private vessel. [link, map] 7. Fort Boyard, France link Fort Boyard is a fort located between the Île-d'Aix and the Île d'Oléron in the Pertuis d'Antioche straits, on the west coast of France. Though a fort on Boyard bank was suggested as early as the 17th century, it was not until the 1800s under Napoleon Bonaparte that work began. Building started in 1801 and was completed in 1857. link Fort Boyard is oval-shaped, 80 metres (260 ft) long and 40 m (130 ft) wide. The walls were built 20 m (66 ft) high. At the centre is a yard, and the ground floor provided stores and quarters for the men and officers. The floor above contained casemates for the emplacements of guns and further quarters. Above that were facilities for barbette guns and mortars. [link, map] 8. Fort Alexander, Russia link Fort Alexander is a naval fortress on artificial island in the Gulf of Finland near St. Petersburg and Kronstadt. In 1899–1917, the fort housed the research laboratory on plague and other bacterial diseases. link It is an oval-shaped building with a yard in its center. The building measures 90 meters (295 ft) by 60 meters (197 ft), with three floors. The overall floor space is over 5000 sq. meters (1.24 acres). The room in the fort was sufficient to hold a garrison of up to 1000 men. There are 103 cannon ports with additional space on the roof for 34 guns. [link, map] 9. Fort Louvois, France link Fort Louvois is a sea fort built on a submerged rock between Oléron Island and the Marennes Basin. It was built from 1691 to 1694 according to plans drawn up by Vauban, the famous military engineer who served under Louis XIV. Taking the form of a horseshoe-shaped outer wall with a central tower protected by a drawbridge and moat, the fort is reminiscent of a medieval castle. link Fort Louvois was designed to protect the southern approach to the Charente estuary by catching enemy ships in a crossfire with the citadel at Oléron. This prevented an enemy from sailing up the river to attack the naval dockyards at Rochefort. At low tide, the fort is connected to the mainland by a 400-metre (1.300 ft) long causeway. [link, map] 10. Flakfortet, Denmark link Flakfortet is a military based sea fortress that was abandoned back in the 60′s located on the artificially built island of Saltholmreb, in Oresund between Copenhagen and Malmo, about 45 minutes sailing from Copenhagen. The fortress is constructed at a seabed 23 feet (7 meters) below the water surface, at the northern meeting point of the straits Kongedybet and Hollaenderdybet. link Flakfortet was built from 1910 to 1915 as part of Copenhagen’s sea-fortifications partly from material excavated from Frihavnen. It was the largest sea fortress in the world, and remains the largest completely man-made true island with the area, including wave breakers, of approximately 70 000 sq meters (17.3 acres). [link, map]