The Castle of Zafra is a 12th-century castle located in the municipality of Campillo de Dueñas, in the Spanish province of Guadalajara. Built in the late 12th or early 13th century on a sandstone outcrop in the Sierra de Caldereros, it stands on the site of a former Visigothic and Moorish fortification that fell into Christian hands in 1129. It had considerable strategic importance as a virtually impregnable defensive work on the border between Christian- and Muslim-ruled territory. It was never conquered and was successfully defended against the king of Castile in the 13th century, but by the end of the 15th century, it had lost its military significance.Photograph credit: Diego Delso