Kaltehofe Waterworks, Hamburg

Hamburg learned the lesson at the worst possible price. In 1892 it and neighboring Altona both drew water from the Elbe, but only Altona passed its supply through sand. More than 8,000 Hamburg residents died of cholera in about three months, most of them within a few weeks, and Robert Koch observed that the epidemic went right up to the Altona boundary and stopped, the two districts differing in one thing only: their water. The city's response was this filtration plant on the island of Kaltehofe, designed by Franz Andreas Meyer, planner of the Speicherstadt, and running from May 1893. Its old filter basins survive in a park on the island, a rare chance to see a nineteenth-century water defense laid out in the open.