With origin as an Iron Age II settlement, Santa Criz de Eslava was a Roman civitas in the Vascones' territory with an economy based in agriculture. The ampliation of the city walls during the Late Republic shows the territorial importance that the city reached in the center of the Ebro Valley and its well-connected position concerning the road-system. During that Roman period the city covered 13 Has. Integrated in the conventus Caesaraugustanus, in the Augustan times the city began to undertake important public works leading to its urban development. Recent archaeological excavations (2007-2016) has discovered the cryptoporticus, which sustained the porticoes of the south side of the forum, and its adjacent depot. A complete study of the architectonic structure and its decoration allow us now to the whole analysis of both its function and its final aspect, the fixing of its early stage, its reforms and a proposal of reconstruction to the whole public area.