The Culebra Cut, which links Gatún Lake with the Pedro Miguel and Miraflores locks, is a catchy name for a channel that the French started digging. Under the Americans, the canal’s most backbreaking work took place here where hills once stood 160 meters (525 feet) above sea level. Thousands of workers blasted through rock and shale, and shoveled and hauled earth, to create what is essentially an underwater valley as well as a peaceful passageway for passengers.