Standing just outside the town of Welshpool on the Anglo-Welsh border, Breidden Hill is an extinct volcano, rising to 367m. The summit is home to the remains of a British Iron Age hillfort, thought to have been the site of the last stand of Caractacus. At the very top of the hill stands Rodney's Pillar, built by the residents of Montgomeryshire who supplied oak wood from the area and shipped it down the River Severn to Bristol where Admiral Rodney's naval fleet was being built. Today, Rodney's Pillar is used as a navigational aid by helicopter pilots, due to its visibility from many miles around.