Narrows of the Forest
The Narrows of the Forrest was the "waist" of Mirkwood caused by the indentation of the East Bight. On the western side of the forest there was a matching natural indentation in the borders of the woods, but the East Bight had been produced by the felling of trees by the Northmen. Together these two indentations narrowed Mirkwood to less than 100 miles at this location and thus afford a means to traverse the woods.
In the time of Forthwini of the Éothéod his realm was troubled by raids by Wainriders who came through the Narrows as well as up the Vale of the Anduin. These incursions prompted Forthwini to send a warning to King Ondoher that the Wainriders had recovered their strength.