Particularly interesting is the 11th-century donjon (keep) that formed part of the town's southern defenses.
The donjon lied isolated from other settlements, a lone watchtower among the foothills. 
mnli hypothesis: The donjon lied isolated from other settlements, a lone watchtower among the foothills.  premise: Particularly interesting is the 11th-century donjon (keep) that formed part of the town's southern defenses.