Wetlands on the southern border of Eriador. Swanfleet was a region of swamps, pools, and eyots - or small islands. Many water birds lived there among the reeds, particularly swans.
The Glanduin flowed west from the Misty Mountains into the wetlands of Swanfleet. At its eastern end, the waters of Swanfleet merged with the River Hoarwell and formed the Greyflood. The city of Tharbad was located near this juncture. The construction of Tharbad had required drainage and the building of dikes, but by the end of the Third Age, Tharbad was deserted and the area had returned to wild wetlands.
On their way home in September 3019 of the Third Age, Frodo Bagginsand his companions crossed the Glanduin and saw the meres and eyots of Swanfleet away to the west.