As perfectly circular as it is redundant, this crater-like artificial island was built in the 1970s to test the feasibility of an ultimately unfeasible engineering project. Because of the concentric pond at its center, the locals dubbed it “the Donut.”

In 1972 the British government commissioned an ambitious engineering project within one of England’s largest bays, the shallow and treacherous Wash. The idea was to build a tidal barrage and power station, along with a freshwater reservoir, to capture the outflow of the river Nene.

Construction began in 1975. Two test islands, including the 820-foot diameter “donut,” were built to investigate the eventual water quality in the reservoir constructed on the former seabed. The island is composed of dredged sand and braced by limestone gabions, or cages filled with rocks, and has a 2.5-acre central reservoir. The test cost £3 million and demonstrated that the project would prove both costly and impractical, as the central reservoir quickly became undesirably salty and silty.

The whole project was abandoned in 1976, but the island stubbornly still exists as a reminder of its failure. 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. The Donut is clearly visible on satellite imagery in which it resembles a marshy meteor-strike in a corner of the bay. The island is now part of the Wash National Nature Reserve and has a new lease on life, as up to 3000 seabirds have made it their home.