Eithel Sirion

Eithel Sirion was the source of the great river Sirion, which flowed eastward at the base of Ered Wethrin to the Fens of Serech. Barad Eithel, the chief fortress of Fingolfin and his son Fingon, was located at Eithel Sirion along with other forts and defenses.

History
During the Dagor-nuin-Giliath, an army of Morgoth's orcs was waylaided by Celegorm, who drove them to the Fens of Serech. 

During the Siege of Angband, Eithel Sirion was used by the Elves of Hithlum to keep watch over Morgoth until the Dagor Bragollach, in which hosts of Orcs broke the siege and nearly defeated the Elves of Fingolfin and Men of Hador. Hador and his son Gundor fell to the onslaught before Eithel Sirion, but ultimately the Elves and Men prevailed and the fortresses at Ered Wethrin remained unconquered. Despite this, Fingolfin rode forward to Angband and challenged Morgoth to single combat. Though he fought valiantly, he was eventually overcome and killed.

Seven years later a force of Morgoth besieged Eithel Sirion. Galdor son of Hador perished in its defense. His son Hurin took his place and drove the Orcs from Eithel Sirion and the surrounding fortresses.

In the Nírnaeth Arnoediad, by the advice of Húrin, the eastern force of Elves and Men stayed back at Eithel Sirion and the surrounding hills. However, Morgoth sent out riders before Barad Eithel with their prisoner Gelmir; they cruelly put him to death in the sight of the Elves. Filled with outrage, Fingon's army charged forward onto the plains of Anfauglith.