From this we learn that Nidhögg resides near Loki’s place of imprisonment and the river Slid whose eddies whirl with weapons. North on a plain called Niðavellir, “Nidi’s fields” are found the golden hall of the dwarf Sindri (a son of Mimir, and maker of Thor’s hammer, cp. Grímnismál 33), and  a “beer-hall” belonging to the giant Brimir (a name of both Mimir—the famous mead drinker of the mythology, Völuspá 28— and his father Ymir, the primeval giant).  Nearby, a hall stands on a beachhead, designated as the Náströnds, “Corpse-shores”. The doors of the hall open north, onto a dark sea, “far from the sun”. Inside the hall constructed of woven serpents, the worst kinds of sinners are showered with venom. There Nidhögg sucks the bodies of the náir (“Corpses”).
 
From this its clear that Nidhögg dwells in the most northern parts of the underworld. It’s clear that his home is not Hel, the kingdom of death to which all men must come (Fafnismál 10), but Niflhel, the place reserved for the worst of creatures.

 After the new earth, teeming with life, has risen from the sea, the dark dragon Nidhögg comes flying up from Niðafjöll (Nidi’s mountains). He bears a corpse (nái) on his wings, flying over the plain (compare Völuspá 39: Nidavellir, “Nidi’s plains”). 

  
Once in the land of death, Skirnir  says that Gerd will sit "on the eagle's perch" looking out of the world she is in “at Hel.” So it’s clear that, although dead, Gerd will not be sent to Hel, but another place, from which she can see Hel. That place is Nifhel, the destination for her kin.  By comparison to it, she will long to be in Hel.

Skirnir informs Gerd that he will send her  "down below the Nágrindr (Corpse-gates)", to a land inhabited by Hrim-þursar, “frost-ogres”, beneath one of Yggdrasil’s roots:

 
 Here the serpents of Niflhel are collectively called “Von’s dragons”. They descend on the newly arrived souls, swarming like flies.  No doubt to feed on those wretched souls intended for the places of eternal punishment.  we are told that Nidhögg feasts on náir. From Gylfaginning 36, we learn that Von is the name of the river formed from Fenrir’s slaver, after the gods chain him with the unbreakable fetter Gleipnir; and in Lokasenna 41, Frey says the gods will chain Loki near his son Fenrir,  directly refering to the river of slaver which shall run from his mouth. As we have already found Loki chained in the vicinity of the serpent infested hall on the Naströnds, "Von's dragons" can be nothing other than the mass of serpents found in Niflhel. [Note: Glævald, "the Prince of Slendor" is otherwise unknown. I suspect this is a reference to Mimir, as ruler of the 'glittering plains' (cp. Glæsisvellir)].

We find support of these conclusions in Book 8 of Saxo's Danish History. There, human adventurers arrive by ship to a place much like the one described above. In other words, they approach by sea and enter the hall on the Naströnds from the northern side, the one facing the darkened sea as described in Völuspá 38 (above).

After sailing for some time into a forbidding, darkened sea, having left the light of the sun and stars far behind:
 
“Then, when they were beginning to be in utter despair, a gleam of unexpected help relieved them, even as the string breaks most easily when it is stretched tightest. For suddenly the weary men saw the twinkle of a fire at no great distance, and conceived a hope of prolonging their lives. Thorkill thought this fire a heaven-sent relief, and resolved to go and take some of it. To be surer of getting back to his friends, Thorkill fastened a jewel upon the mast-head, to mark it by the gleam. When he got to the shore, his eyes fell on a cavern in a close defile, to which a narrow way led. Telling his companions to await him outside, he went in, and saw two men, swart and very huge, with horny noses, feeding their fire with any chance-given fuel. Moreover, the entrance was hideous, the door-posts were decayed, the walls grimy with mould, the roof filthy, and the floor swarming with snakes; all of which disgusted the eye as much as the mind.
 
"…Thereupon Thorkill took the fire along to his companions; and finding a kindly wind, landed on the fourth day at the appointed harbour. With his crew he entered a land where an aspect of unbroken night checked the vicissitude of light and darkness. He could hardly see before him, but beheld a rock of enormous size. Wishing to explore it, he told his companions, who were standing posted at the door, to strike a fire from flints as a timely safeguard against demons, and kindle it in the entrance.
 
"Then he made others bear a light before him, and stooped his body through the narrow jaws of the cavern, where he beheld a number of iron seats among a swarm of gliding serpents. Next there met his eye a sluggish mass of water gently flowing over a sandy bottom. He crossed this, and approached a cavern which sloped somewhat more steeply. Again, after this, a foul and gloomy room was disclosed to the visitors, wherein they saw Utgarda-Loki, laden hand and foot with enormous chains. Each of his reeking hairs was as large and stiff as a spear of cornel. Thorkill (his companions lending a hand), in order that his deeds might gain more credit, plucked one of these from the chin of Utgarda-Loki, who suffered it. Straightway such a noisome smell reached the bystanders, that they could not breathe without stopping their noses with their mantles
 
"They could scarcely make their way out, and were bespattered by the snakes which darted at them on every side. Only five of Thorkill's company embarked with their captain: the poison killed the rest. The demons hung furiously over them, and cast their poisonous slaver from every side upon the men below them. But the sailors sheltered themselves with their hides, and cast back the venom that fell upon them. One man by chance at this point wished to peep out; the poison touched his head, which was taken off his neck as if it had been severed with a sword. Another put his eyes out of their shelter, and when he brought them back under it they were blinded. Another thrust forth his hand while unfolding his covering, and, when he withdrew his arm, it was withered by the virulence of the same slaver."
 
This is clearly the same place described in Völuspá 35-39. Thorkill and his men arrive on a sunless sea, much like the one described there. Near the beachhead, a hall (in Saxo, a cavern) stands writhing with venomous serpents. Its doors open north, onto a dark sea, “far from the sun”. The soot of ages covers the doorposts. Inside, they see rows of iron seats (likely for the various types of sinners named in Völuspá 38). They likely sit according to rank, the most despicable nearest the floor. The whole lot is spewed from above with serpent venom, which runs in a sluggish mass onto the floor.