By hello
A former Thames tributary now hidden below west London. It rose near Hampstead, fed the line of the Serpentine, then continued south under Chelsea. Status: Culverted and incorporated into drainage infrastructure Surface clues: Its course can be traced through Bayswater, Hyde Park, Knightsbridge, and Sloane Square Best-known remnant: The river still crosses Sloane Square station in a visible iron conduit above the platforms