Harry's Walls are the remains of an unfinished artillery fort, started in 1551 by the government of Edward VI to defend the island of St Mary's in the Isles of Scilly. Constructed to defend the harbour of Hugh Town from possible French attack, the fortification incorporated Italianate-style bastions with protective orillons and would have been the most advanced design in the kingdom at the time. It was not completed, probably due to a shortage of funds and the passing of the invasion threat, and only the south-west side remains. In the 21st century, Harry's Walls are managed by English Heritage and open to visitors.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.