A causeway is a road or railway route across a broad body of water or wetland raised up on an embankment. Some causeways may only be usable at low tide and the distinction between causeways and viaducts can become blurred when flood-relief culverts are incorporated in the structure; a causeway is however primarily supported on earth or stone, whereas a bridge or viaduct is mainly supported by free-standing columns or arches.
# Great Salt Lake Causeway, USAThe causeway running across the Great Salt Lake, Utah, was built in the 1950s by the Morrison-Knudsen construction company for the Southern Pacific Railroad as a replacement to a previously built wooden trestle, and is now owned and operated by Union Pacific. About 15 trains cross the 20-mile (32km) causeway each day. Because water flow is so constrained by the causeway, it has a significant impact on various industries. The salt discrepancy is visible to anyone who flies over the causeway. The water on the north side usually has a distinct reddish tint, while on the south side it's greenish-blue. The colors are attributed to different species of algae that thrive in different concentrations of salt.
# Hindenburg Dam, GermanyHindenburg Dam is an 11 km-long (7mi) causeway joining the North Frisian island of Sylt to mainland Schleswig-Holstein. It was opened on 1 June 1927 and is exclusively a railway corridor. A train trip along the causeway takes about 10 minutes, and the time between the auto terminals at Niebüll on the mainland and Westerland on Sylt is about 30 minutes. The Hindenburg Dam is part of the railway line known as the Marschbahn (Marsh Railway), which is double-tracked along much of the route, although there as yet exists a single-tracked stretch. On the causeway is a signal box. Every day, more than 100 trains pass over the causeway, 50 of those ferrying cars (there is no road link to Sylt).
# Passage du Gois, FranceLe Passage de Gois ou Gôa is a natural, periodically flooded causeway leading to the island of Noirmoutier in France. It is located between Île de Noirmoutier and Beauvoir-sur-Mer, in the department of Vendée. Causeway is flooded twice a day by the high tide. Every year, a foot race – the Foulées du Gois– is held across it, starting at the onset of the high tide. In 1999 Passage du Gois was used by Tour de France bicycle race during Stage 2. It proved to be decisive for the race after a fall took place because of its slippery surface.
# Funafuti Causeway, TuvaluMade up of four coral islands and five atolls off the coast of Australia, Tuvalu has a maximum height of only 4.5 meters (15 feet) above sea level. There's a section on island of Funafuti where the island was too narrow for a road, so they built this concrete section that they refer to as the causeway. This causeway is quite important for local traffic, because it connects the northern and southern part of the island. As you can see in the picture above, waves often wash over this causeway.
# Causeway Between Jindo and Modo Islands, South KoreaThe tide-related sea level variations result in a local phenomenon (a Moses Miracle) when a land pass 2.9 km (1.8 mi) long and 10–40 meters (11-33 yds) wide opens for an hour between Modo and Jindo islands (Jindo County, South Jeolla province). The event occurs approximately twice a year, around April-June. It had long been celebrated in a local festival called Jindo's Sea Way, but was largely unknown to the world until 1975, when the French ambassador Pierre Randi described the phenomenon in a French newspaper. Nowadays, nearly half a million foreign and local tourists attend the event annually.
# Rough Island Causeway, UKRough Island is accessible across the causeway from Kippford when the tides allow or across the mudflats from Rockcliffe, the isle of Rough can be walked to from the Scottish mainland. As the island is a bird sanctuary visitors should avoid travelling to the island during the months of May and June to avoid disturbing the nesting oystercatchers and ringed plovers. The islands' causeway is flooded and underwater for 5 (five) hours during high tide and visitors to the island need to take this into account when travelling there.