On the hills around Forteviot there is a remarkably dense concentration of hillforts. They are diverse in form, size and location. The ramparts were constructed in stone or earth, sometimes both. They can have a single defensive circuit or several; they can accommodate one dwelling or many; and the choice of hill-slope can be gentle or extreme. This variation testifies to a long chronology but until the current investigations even the dating was uncertain.
We now know that the main period of hillfort construction ran from the late Bronze Age (c. 1200 BC) until the late Iron Age (c. 200 BC). There were later periods of hill top fortifications, including during the Roman period (1st and 2nd centuries AD) and in the medieval period. The broch on Castle Craig was built within an Early Iron Age hillfort and refortified again in the 10th century.