The Anduin was the mightiest river in western Middle-earth. Rising near the slopes of the Grey Mountain , the Anduin travelled through many lands before it emptied into the Bay of Belfalas in southern Gondor . Only one bridge, at Osgiliath , crossed the Anduin. Another existed by the Iach Iaur but it had fallen into disrepair, and if when it still stood, it was dangerous to traverse. Fords and ferries at Tir Anduin, Iach Iaur, and Maethelburg provided the only other safe crossings. Difficult fords could be found at the Carrock and in the Wold . Those wishing to cross elsewhere were wise to construct a sturdy vessel first, for the Anduin's current was powerful and unpredictable, even where it did not flow swiftly. All folk in Middle-Earth knew the sad tale of how Isildur sank beneath the powerful current as he fled an Orcish ambush at the Gladden Fields. Traffic on the Anduin was still quite common , especially where it passed through Gondorian lands. Large ships could travel all they way to the Undeeps, though most sea-going vessels unloaded their wares at Harlond. The Falls of Rauros were an obstacle to passage into northern Rhovanion, and one usually changed to small river-craft there. Travel north of the Rauros was occasionally dangerous, due to the swift currents fed by run-off from the mountains. A traveller would be prudent to hire an experienced guide before testing the dangers of the Anduin . As perilous as it may have been, the river remained the safest avenue to the North , for no right-thinking Man would risk passing under the wood of Lothlorien or the shadow of Dol Guldur.
The great river flowed through the heart of southern Gondor, watering the verdant lands of Lebennin, Ithilien and arid northwestern Harondor on its long journey to the sea .The width of the Anduin increased at a fairly regular pace, growing from a half mile at the Great Bridge of Osgiliath to nearly a mile and a half at Pelargir, below which it began to broaden dramatically, reaching a width of forty-six miles at the Ethir, where it emptied into Belfalas Bay. The river was navigable throughout southern Gondor by any craft or vessel, since it had an average depth of thirty feet. Only in the Ethir was it necessary for a larger ship to be steered by trained pilots away from sandbars and other obstacles. But even there the main channels of the river were deep year-round; because it was fed by so many sources, the Anduin never lost its depth—and during the spring, when the Great River's mountain-fed sources swoll from the melting snows, the waterlevel did sometimes rise a foot or two. The river was tidal up to the Loeg Balimur, affecting the lowlands of Lebennin, northwestern Harondor, and especially the Ethir . The Anduin teemed with life,and as such it was a major source of subsistence and livelihood for those who lived on or close to its banks.Fishing was practiced along the Anduin Throughout southern Gondor, which meant that there were alwaysn rivercraft available for ferryingTravelers, though only with regular ferry services could one be assured of an affordable price (the locals having been invariably shrewd when it came to bargaining for the use of their precious boats).