What is "chemin de ronde"

n. A raised protected walkway behind a castle battlement.

A chemin de ronde ( French, "round path"' or "patrol path"; )—also called an alure, allure or, more prosaically, a wall-walk—is a raised protected walkway behind a castle battlement.

In early fortifications, high castle walls were difficult to defend from the ground. The chemin de ronde was devised as a walkway allowing defenders to patrol the tops of ramparts, protected from the outside by the battlements or a parapet, placing them in an advantageous position for shooting or dropping.