The ruins of the Fort Bernia have recently been tidied up with notices describing the ramparts etc. There is also a nice profile of the mountain ranges off to the south so you can identify the peaks.
According to oft quoted accounts in English tour guides, The fort on Bernia was built in 1565 and was once an important stronghold which housed a substantial garrison. It was devastated in 1612 by Philip III who ordered its demolition after he captured it from the Moors. However, see our History file for another more mundane story!