ABSTRACT: Viaduct over the river Ulla constitutes the most important intervention in the High Speed Atlantic Railway Line between A Coruña and Pontevedra, in Galicia. The viaduct is 1620 m long with a span distribution of 50 + 80 + 3 × 120 + 225 + 240 + 225 + 3 × 120 + 80 m, which means that the main span is about 20% longer than the current world record, the Nantenbach bridge over river Main in Germany (208 m long span). The main spans are resolved with a double truss depth-varying deck, with a depth ranging from 8.5 m at the midspan to 17.25 m at the section over the piers. The article describes the structural conception of the bridge and the three different constructive processes used for erecting the deck: erection of the 5 central spans by 4 equilibrated cantilevers, launching of the four lateral spans nears abutment 1 and the complete lifting of the three lateral spans near abutment 2.