The World's Most Expensive Forgotten Edifices

11. Ruins of the McMillan Sand Filtration Site

Location: United States, Washington, D.C. Year: 1986 (Government Purchased) Cost: The 1986 purchase price of $702 million* The McMillan Sand Filtration Site, as its name would imply, used nothing but sand to filter water for the Washington, D.C., area. This public enterprise was constructed during the Industrial Era. McMillan was essential to Washington, D.C., which suffered from unclean, unfiltered Potomac water tainted with microorganisms that led to a high rate of illness.

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Atlasobscura/Pinterest: Ruins of the McMillan Sand Filtration Site McMillan filtered the water using sand from Laurel, Maryland, and the filtration site enhanced the state of Washington's water quality. McMillan was neglected as technology developed and evolved. Even though the D.C. government purchased the area in the middle of the 1980s, they disregarded local historical protection associations' demands and did not maintain McMillan in excellent condition.