▁stones ▁is ▁laid ▁length wise , ▁and ▁the ▁next ▁layer ▁has ▁the ▁ends ▁facing ▁out wards ▁ ▁St ones ▁linked ▁with ▁do vet ail ▁joint s ▁or ▁metal ▁bars ▁ ▁Ind ents ▁in ▁the ▁stones ▁for ▁g ri pping ▁tools ▁to ▁hold ▁on ▁to ▁( Source ▁Tra ian us ▁– ▁An ▁endeav our ▁to ▁identify ▁Roman ▁Br id ges ▁built ▁in ▁former ▁His p ania ) ▁ ▁Op us ▁pont is ▁▁ ▁The ▁costs ▁of ▁building ▁and ▁repair ing ▁brid ges , ▁known ▁as ▁op us ▁pont is ▁(" bridge ▁work "), ▁were ▁the ▁responsibility ▁of ▁multiple ▁local ▁municipal ities . ▁Their ▁shared ▁costs ▁prove ▁Roman ▁brid ges ▁belonged ▁to ▁the ▁region ▁overall , ▁and ▁not ▁to ▁any ▁one ▁town ▁( or ▁two , ▁if ▁on ▁a ▁border ). ▁The ▁Alc ánt ara ▁Bridge ▁in ▁L us it ania , ▁for ▁example , ▁was ▁built ▁at ▁the ▁exp ense ▁of ▁ 1 2 ▁local ▁municipal ities , ▁whose ▁names ▁were ▁added ▁on ▁an ▁ins cription . ▁Later , ▁in ▁the ▁Roman ▁Empire , ▁the ▁local ▁l ords ▁of ▁the ▁land ▁had ▁to ▁pay ▁t ith es ▁to ▁the ▁emp ire ▁for ▁op us ▁pont is . ▁The ▁Ang lo - S ax ons ▁continued ▁this ▁practice ▁with ▁br ic g - gew or c , ▁a ▁literal ▁translation ▁of ▁op us ▁pont is . ▁ ▁Ex amples ▁ ▁For ▁out standing ▁achiev ements ▁of ▁Roman ▁bridge ▁building , ▁see ▁List ▁of ▁ancient ▁architect ural ▁records . ▁ ▁Bu ilt ▁in ▁ 1 4