But as Glaurung was passing over Narog, Mablung drew aside and lay under a rock, and remained; for it seemed to him that he had an errand yet to do. He knew now indeed that Glaurung abode in Nargothrond, but he was bidden also to learn the truth concerning Húrin’s son, if he might; and in the stoutness of his heart, therefore, he purposed to cross the river, as soon as Glaurung was gone, and search the halls of Felagund. For he thought that all had been done that could be for the keeping of Morwen and Niënor: the coming of Glaurung would be marked, and even now the riders should be speeding towards Doriath.
  Glaurung therefore passed Mablung by, a vast shape in the mist; and he went swiftly, for he was a mighty Worm, and yet lithe. Then Mablung behind him forded Narog in great peril; but the watchers upon Amon Ethir beheld the issuing of the Dragon, and were dismayed.

“The Journey of Morwen and Niënor to Nargothrond” - The Children of Húrin - J.R.R. Tolkien

Finrod’s Adventure

Finrod: *finds his way to Doriath*
Galadriel: *hi me too*
Finrod: Man, Menegroth is way cool. They have treasuries and armories and … stuff.
Thingol: How you guys doing. Can I offer you some snacks. Maybe a soda.
Finrod: Yo, Thingol. Can I level with you for a sec.
Thingol: Sure. Wuddup, meng.
Finrod: *tells him about the Ulmo dreams*
Thingol: … so uh, come with me. *takes him the gorge of the River Narog*
Finrod: Neat –
Thingol: *gives him specific directions* And uh .. good luck. Peace. *back up to safety*
Finrod: … damn it, Thingol.

Finrod's Adventure Part 2

Finrod: *finally somehow majestically makes it to the Caves of Narog*

Finrod: … hmm. This would be cool to make a replica of Menegroth here.
Dwarves: hey man. I heard you want to build things.
Finrod: Oh, hey. You’re from the Blue Mountains.
Dwarves: Yep. We totally helped make Menegroth too.
Finrod: Oh sweet. Hey, help me make another Menegroth. But we’ll call it … uh … Narogthong … or .. hm .. that sounds silly. How about Nargothrond?
Dwarves: Sure.
Nargothrond: *is built*
Finrod: *gets some sweet fuckin gifts for the dwarves from Tirion, the watch-tower*
Finrod: Hey guys, this is for you.
Dwarves: *AWE*
Dwarves: Look, we made a thing for you. *gives him the Nauglamir* King Felagund!
Finrod: My name’s Finrod –
Dwarves: Felagund! Felagund!
Elvish Followers: That has a nice ring to it. Felagund, yo!
Felagund: … okay. Finrod Felagund it is.

No eyes them watched    onward wending
till they gained the gorge    where Ginglith turns
all glad and golden    to greet the Narog.
There her gentler torrent    joins his tumult,
and they glide together    on the guarded plain
to the Hunters’ Hills    that high to southward
uprear their rocks    robed in verdure.
There watchful waited    the Wards of Narog,
lest the need of the Gnomes    from the North should come,
for the sea in the South    them safe guarded,
and eager Narog    the East defended.
—  J.R.R. Tolkien, The Lay Of The Children Of Húrin