TheAdda (Latin: *Abdua*, or *Addua*; Lombard: *Ada*, or *Adda*) is a river in NorthItaly, a tributary of thePo. It rises in theAlps near the border withSwitzerland and flows throughLake Como. The Adda joins the Po nearCastelnuovo Bocca d'Adda, a few kilometers upstream ofCremona.[2] The river's length is 313 kilometres (194 mi). The highest point of thedrainage basin is the summit ofLa Spedla (a subpeak ofPiz Bernina), at 4,020 metres (13,190 ft).
The Adda's source is in the Alpisella valley near the head of the Fraele glen, within theRhaetian Alps.[1] Its flow is augmented by several smaller streams nearBormio. From there, it flows southwest, then west, through theValtellina, passingTirano, where thePoschiavino joins from the right, andSondrio, where theMallero joins, also from the right. This section of the Adda's course is unusual in Northern Italy, as it flows from east to west. The river flows into the northern end of LakeComo, contributing significantly to the lake's volume. Exiting the lake's southeastern (Lecco) arm, it crosses the Lombardy Plain. It receives water from theBrembo andSerio from the left, and ultimately joins thePo.[3]
TheTrezzo sull'Adda Bridge, constructed in 1377, had a single arch of 72 metres (236 ft), the longest bridge arch built before the introduction of metal in bridge construction.[4]
The lower course of the Adda historically marked the border between theRepublic of Venice and theDuchy of Milan, as established by theTreaty of Lodi in 1454. Several significant battles have been fought along its banks, including theBattle of Lodi in 1796, whereNapoleon defeated Austrian forces.[3] The bridgehead atCassano d'Adda and its surrounding area have also been the site of multiple battles, including one in 1705 involvingPrince Eugene of Savoy and the French, and another in 1799 whereAlexander Suvorov led his forces across the river.[3]
