The relative absence of written references to fortifications in the Carolingian Empire is well known, but seems difficult to square with increasing evidence that such buildings were familiar features in the ninth-century Frankish landscape. I argue that one reason for this is that contemporary narratives participated in a Carolingian “way of seeing” which associated castle building with frontier territories and lands beyond rather than with the imperial heartlands. Fortified residences were linked in the Carolingian imperial imagination with negative characteristics such as secrecy and hiddenness, in contrast to the supposed openness of Frankish royal palaces.