The document provides information about Conisbrough Castle, including its timeline, owners, and features. It discusses:
- The castle was originally built in the 11th century and expanded in the 12th century under Hamelin Plantagenet with the addition of the unique cylindrical stone keep.
- The keep is a landmark structure standing 90 feet tall with thick walls and several levels that would have provided last line of defense if the castle walls were breached.
- Over subsequent centuries the castle changed ownership and fell into disrepair before being acquired by the local council in 1920 and cared for by English Heritage.