According to clues given by the geographer Ptolemy, the Caledoni tribe inhabited the inland parts of central Scotland to the east of the Great Glen Fault, encompassing the north Central Region, west Tayside, south-west Grampian and south-east Highland Region. The entire tribal territories are characterised by mountains, the Monadhliath in the north-west, the Cairngorms in the north-east and the Grampians, including Ben Nevis, in the south. The tribe was bordered on the east by neighbouring tribes occupying the relatively rich coastal lands, the Taexali on the north-east coast, the Vacomagi to the east and the Venicones to the south-east. The Damnoni of southern Strathclyde held territories to the south, across the Clota Aestuarium (Firth of Clyde), and the Epidii situated on the Mull of Kintyre were separated from the Caledoni by their remote location.
The Caledoni were never brought under direct Roman rule, therefore we may safely assume that a Romanised tribal centre, a Civitas Caledonorum, did not exist. Ptolemy mentions no tribal centres at all, although that is not to say that none were present.
Although it is possible that the Romans conducted some exploration of the Caledonian tribal territories, no marching camps have been discovered in testament to their passing through the area, all Roman Military operations being confined to a narrow strip along the north-east coast of Scotland through the lands of neighbouring tribes. Given this absence of archaeology, we may conclude that the lands of the Caledoni lay completely outside the Roman military's sphere of operations in Britain.
It is almost certain that the Roman Legionary Fortress at Inchtuthil was built as a prelude to major campaigns directed against the Caledoni tribe, but it is very likely that this military establishment was sited within the disputed territory between the Venicones and the Vacomagi tribes, not in the lands of the Caledoni themselves.
It is fairly certain that the so-called 'Glen-Blocking Forts' were constructed as a defense against incursions along the valleys leading from the Caledonian interior. These forts are all located along the border between the Caledoni and the Venicones to the south-west of the Inchtuthil fortress, probably just within the territories of the latter tribe; listed from south to north, they are:
... Calgacus is the only northern british tribal leader known by name to the Romans. ...