In the Middle Ages the area was only sparsely inhabited but some castles were constructed nearby like Hohenneuffen Castle (early 12th century) or Burg Hofen east of Grabenstein. The purpose of a medieval fortification surrounding 55 hectares to the north of Heidengraben (known as Bassgeige) is still unknown. It incorporates parts of a Celtic wall but was extended in late medieval times. Several similar structures nearby (Brucker Fels and Beurener Fels) also served an unknown purpose.: