 This is also associated with a slight rise in sea level that may explain the lack of evidence for low-lying settlements.There is sparse evidence for the Late Iron Age and early Romano-British periods.Nevertheless, enclosures seen from aerial photography in upland areas such as Crosby Garrett and Crosby Ravensworth, together with similar evidence from the Solway Plain and Eden Valley, (see the section below on Life in Roman Cumbria for a listing of the main sites), point to the populous nature of the territory held by the Brigantes (as noted by Tacitus in the 'Agricola').