The Calisio, whose top measures 1096 m, closes the Adige valley to the north-east of the city: it is also called Argentario because of its ancient silver mines. Its slopes were already fortified between 1869 and 1872 with the Civezzano barrage, which consisted of two road blocks (fortified blockade) and the main fort. Then, in the 1880s, the Martignano and Casara batteries were built. In 1915, cima Calisio, which already housed batteries and an observatory, was completely fortified. The Trento military engineers built an underground fortress: one of the most modern and largest works in the fortress. Walking towards the top of the mountain, one finds caves, remains of trenches and casemates for machine guns, infantry outposts and positions for field artillery: the traces of the great defence system are still easily recognisable. The panorama from the summit, although modest in altitude, sweeps over the Adige valley, the other mountains surrounding Trento, the upper Valsugana and the Lagorai.
