The monument in the Nero Valley commemorates the state geologist Karl Koch, who planned the construction of deep tunnels for Wiesbaden's water supply. In gratitude for his achievements, the city and many of his companions financed the Carl Koch monument, which was inaugurated at the foot of the Speierkopf in 1883. It was created by the Wiesbaden sculptor Hermann Schies. The granite obelisk (Taunusstein) stands on a stepped base. At the front is a medallion with Koch's portrait. The pedestal bears the dedication: "To the memory/of the state geologist Dr. Carl Koch/Dedicated by his friends, colleagues and students 1883".