The Taurini controlled the main Roman route from Italy to Gaul through the western Alps, the Val di Susa to the Col de Montgenèvre (1,850m). The latter was accessible for a longer period in the year than the other western passes, due to its relatively low altitude. This was the most likely route followed by the Carthaginian general Hannibal when he led his army across the Alps in 218 BC. This area formed the Alpes Cottiae province, named after the local king Cottius, who initially resisted Augustus' imperialism but eventually submitted and became the emperor's ally and personal friend. His territory, together with that of the other Alpine tribes, was annexed to the Roman empire in 15 BC - although Cottius, and his son after him, were accorded the unusual privilege of continuing to govern the region, with the title of praefectus i.e. Roman governor. In 8 BC, Cottius showed his gratitude for this reprieve from dynastic oblivion by erecting a triumphal arch to Augustus in his capital, Segusio (Susa, Piedmont, Italy), which still stands. After the death of Cottius' son, the emperor Nero (ruled 54-68) appointed a regular equestrian procurator to govern the province.