The Broad Street Pump, John Snow memorial, Broadwick Street (formerly Broad Street) in, London. In 1854 an epidemic of cholera affected residents of Soho district. Dr. John Snow surveyed deaths reported in the homes mostly near the pump and used it for their drinking water. His documented evidence suggested that contaminated water from this pump was the source of the epidemic; he caused removal of the handle, and the already declining epidemic due to people leaving the area, ceased entirely.

Source: Creative Commons photograph by Justine.