In The Wash, a squarish estuary on the East coast of England, where Norfolk meets Lincolnshire, there is a strange island, flawlessly circular, with a dimple in the middle similar to a huge doughnut. This doughnut famously recognized as the “Outer Trial Bank”. This is one of two islands built during the 1970s to study the feasibility of converting the entire estuary into a fresh water reservoir. The other trial bank, built before the Outer Trial Bank, is connected to Norfolk by a causeway on Terrington Marsh.
The island is composed of dredged sand and braced by limestone gabions, or cages filled with rocks, and have a 2.5-acre central reservoir. It’s rarely included on maps even though it stands out as one of the highest points on the otherwise flat, marshy coast of the Wash. It seems various people are inquisitive to what these structures are? What this peculiar structure is out in the Wash – whether a meteor’s landed in the Wash or aliens have landed or something! The numerous thoughts come in mind. The concept of constructed Outer Trial Bank was to build a tidal barrage across half of the Wash to capture freshwater from rivers flowing into the estuary. However, the plan was failed hugely because the banks were built using mud dredged from the salt marsh, which was saline anyway. This is salinated the stored fresh water.
Moreover, the plan was shelved but not after £3 million were spent in unsuccessful. There’re no systematized tours or trips to the island, but you can see online videos which will reveal that it can be reached by some experienced kayakers with knowledge of the tidal conditions in The Wash. They’re very significant as they’re major landforms in the area. They’re the only hills in the Wash. Now these artificial islands have gained novel importance as a breeding bird colony, with around more than 3,000 pairs of sea birds using it as their nest. They’re declining in a lot of their breeding habitats but here they’re doing very well.
Source: Amusing Planet ! Atlas Obscura