Remains of a fortress documented since the early 10th century, located at the top of the rocky outcrop overlooking the village of Castellbò. Since 989, it belonged to the viscounts of Urgell, who took the name Castellbò from then on. Today, only fragments of some walls remain, made of small, irregular stones. It is likely that the original structure was of significant size. On the northern and western slopes of the hill, several thick wall sections made of rough masonry bound with mortar can still be seen. As its name suggests, it originally had a defensive function. It has recently been restored.