Walden Castle

Walden Castle is a Grade I listed remnant of a tower-keep, dating from the late 11th century or early 12th century. The structure has a flint and mortar core, though the walls are severely degraded. It has a rectangular plan, approximately 12.3 meters square, with a northwest projection for a forebuilding. Two storeys remain.

Inside, there is a central pier base that supports the upper floors, and the ground floor features semicircular arched recesses on the north, south, and west sides, each approximately 2.0 meters deep. The south recess displays some herringbone pitched flint work and shuttering ridges in the soffit mortar of the south, southwest, and north recesses. On the first floor, a recess on the west side is interpreted as a fireplace. The walls show breaches at the southeast corner, where stairs have been added, and there is a tunnel at the back of the north recess. A well, now covered, is located in the northwest angle, above which is a low projection built in the 18th century as a semaphore station.

Despite being a ruin, areas of the original flat wall facing with simple flint work remain visible in several locations, including the exterior, the center of the north wall, the outer face of the pilaster buttress, and adjacent walls on the east side, as well as the interior rear wall of the recess in the south wall and the adjacent wall to the east. Some of the walling is covered with ivy.

Historically, it is uncertain who built the keep, but stylistic comparisons suggest it was constructed in the second quarter of the 12th century, similar to Farnham Castle (1138) and Ascot Doilly Castle (1129-1142). Geoffrey II de Mandeville was forced to surrender the castle to Stephen in 1144.