Places in Middle-earth
Meaning: City of Elves
Location: In Eregion along the Sirannon, between the Marsh called Nîn-in-Eilph and the gate of Moria.
Description: "From Ost-in-Edhil, the city of the Elves, the highroad ran to the west gate of Khazad-dûm"
The Silmarillion, Of the Rings of Power and the Third Age
Ost-in-Edhil is located on the north side of the confluence of the Sirannon and the Glanduin, about halfway between where the Glanduin joins the Hoarwell (Mitheithel) and the West-door of Khazad-dûm. It is the western endpoint of the Elven-way (Highroad) from Hollin to Moria.
The Atlas of Middle-earth, Revised Edition, by Karen Wynn Fonstad, Section 4, Regional Maps: The Misty Mountains
Contributors: Lyllyn 7.2.03; added exact location: Elena Tiriel 7.16.04