▁can als , ▁most ▁of ▁which ▁are ▁used ▁for ▁ir rig ation . ▁ ▁The ▁river ▁Po , ▁which ▁is ▁the ▁longest ▁Italian ▁river , ▁is ▁the ▁natural ▁boundary ▁with ▁the ▁ad jo ining ▁Province ▁of ▁P iac enza , ▁while ▁the ▁Og lio ▁separ ates ▁the ▁province ▁from ▁Bres cia . ▁ ▁History ▁Lomb ard y ▁has ▁been ▁inhab ited ▁since ▁ancient ▁times ▁and ▁stone ▁age ▁and ▁Bron ze ▁Age ▁rock ▁draw ings ▁and ▁arte fact s ▁have ▁been ▁found ▁there . ▁From ▁the ▁fifth ▁century ▁BC , ▁Gall ic ▁tribes ▁inv aded ▁and ▁settled ▁in ▁the ▁region , ▁building ▁several ▁cities ▁( including ▁Milan ) ▁and ▁r uling ▁the ▁land ▁as ▁far ▁as ▁the ▁Adri atic ▁Sea . ▁From ▁the ▁third ▁century ▁BC ▁the ▁Rom ans ▁expanded ▁their ▁sphere ▁of ▁influence ▁into ▁the ▁area , ▁and ▁in ▁ 1 9 4 ▁BC , ▁the ▁whole ▁of ▁what ▁is ▁now ▁Lomb ard y , ▁became ▁a ▁Roman ▁province ▁called ▁Gall ia ▁C is al p ina . ▁The ▁Rom ans ▁over wh el med ▁the ▁previous ▁civil is ations ▁and ▁Lomb ard y ▁became ▁one ▁of ▁the ▁rich est ▁and ▁best - develop ed ▁areas ▁in ▁Italy . ▁It ▁was ▁here ▁in ▁ 3 1 3 ▁AD ▁that ▁the ▁Roman ▁Emperor ▁Const antine ▁the ▁Great ▁issued ▁the ▁famous ▁Ed ict ▁of ▁Milan ▁that ▁gave ▁freedom ▁of ▁religion ▁to ▁all ▁people ▁in ▁the ▁Roman ▁Empire . ▁ ▁Following ▁the ▁collapse ▁of ▁the ▁Western ▁Roman ▁Empire , ▁Lomb ard y ▁was ▁inv aded ▁by