of it as being forbidding.  

The mere was quite a distance from Heorot. It says that they must cross a moor, over steep stony slopes, narrow ways, choked paths, gullies, cliff ledges, and haunted lakes to get there.

The area surrounding the mere is referred to as a mountain grove. Above the mere is gray stone with a hanging wood. The water of the mere is dark and dour - meaning rocky and infertile.  The water seethes with blood. The use of the word seethe is interesting because the word requires movement such as a boiling action or an agitation. The water is also referred to as blood red, as the soldiers are waiting for Beowulf's return.  

The surroundings add to the gloom. They find Aeschere's head next to the cliff.  And, as they watch the water, they see serpents, sea-dragons, water daemons, worms and slithering wild things going in and out of the lake.  

Once Beowulf swims to the bottom (remember it took him almost a full day to get to the bottom) he is attacked and dragged into Grendel's Mother's cave. It is full of horrible tusked creatures that attack him.  The cave has an area that keeps the water out and it is lit by firelight. Beowulf likens the space to a hall, so it is quite large. There is pile of weapons forged by giants at the edge of the cave and Grendel's corpse near the wall.  (It is somewhat hidden because Beowulf has to search for it.)  

Several key attributes define this location.

First of all, it is far from human habitation.

Second, it is on the monster's home ground. Remember that Grendel had intruded into where the men were sleeping. In that attack, a monster intruded into the human realm. In this attack, Beowulf, a human, intrudes into the monster's home realm. So, it is a reversal.

Third, it is at the bottom of a lake. This is both a sign of Beowulf's heroic prowess--who but a great hero could hold his breath this long and still fight--and symbolizes the fact that this is Grendel's mother's court. It is a kind of underworld.

Fourth, it is a dark cave full of monsters and other animals. However, the cave is also the site of other battles and trophies: there is a giant sword on the wall (that Beowulf will soon use).

Little is actually written in terms of a full description of the location of this momentous battle. It happens in the depths of the lake that Beowulf dives into and then in the vault that Grendel's mother takes him to. It is clear that both the depths of the lake and the vault are described as very dangerous places that threaten Beowulf's life. Grendel's mother is not the only beast, and as she clutches Beowulf and takes him with her to her underground lair, other creatures try and attack Beowulf:

...a bewildering horde
came at him from the depths, droves of sea-beasts
who attacked with tusks and tore at his chain-mail
in a ghastly onslaught.

The few descriptions that the reader is given of the location of this battle are variously a "hellish turn-hole" and a "vault." It is only after Beowulf has slain Grendel's mother that "The place brightened" and he is able to find his way to Grendel's corpse to behead it, but still little description is given of Grendel's mother's vault. Throughout the main focus is on the titanic clash between Beowulf and Grendel's mother and the allegorical nature of this battle as good meets evil and good finally vanquishes evil.

In Beowulf, the battle with Grendel is set at Heorot, the royal hall of Hrothgar, the Danish king. Prior to Beowulf's encounter with Grendel, the monster had engaged in regular pillaging of Heorot for a considerable length of time (about twelve years, in fact), and he wreaked considerable havoc on Hrothgar's subjects by violently devouring many of them.

The fact that Beowulf fights and defeats Grendel at Heorot is significant. Heorot can be seen to represent civilized order in the midst of wilderness, while Grendel can be seen as the chaotic force attempting to topple said civilization. As such, the fact that Beowulf defeats Grendel at Heorot signifies the return of established order in the face of chaos and disorder. Of course, Beowulf's efforts have only begun after his defeat of Grendel (he still has to face Grendel's mother and the dragon), but his battle at Heorot is his first major victory in the epic.

Beowulf is an epic poem which was first created in the oral tradition centuries ago. Though there are many elements of the story which are not applicable to modern life or readers (such as dragons and superhuman feats), readers are still able to connect to the themes and sentiments of the narrative. Grendel's mother is a good example of a recognizable character despite the fact that she is a 

Devil-shaped woman, her woe ever minded,
Who was held to inhabit the horrible waters.

First of all, Grendel's mother is, of course, a mother. While she is certainly not a typical mother in appearance or in the offspring she produces, Grendel's mother has the same instincts as any modern mother. When her child has been killed, she grieves for him. Grendel left the mead hall and went to his mother to die; the next day, she goes to Heorot to retrieve her son's arm. While the image and the act are both gruesome, her desire to mourn her son and keep his body intact even after death is a universal emotion.

Second, Grendel's mother seeks revenge for her child's death. It is true that she goes to the extreme (kidnaping and killing a man), but the desire to have have someone pay for the untimely death of a child is understandable and even shared by many women (parents) today.

Third, Grendel's mother is willing to fight on behalf of her son. Though Grendel is gone, when Beowulf comes to her underwater den, she fights--and nearly wins--to keep her child's body from being further mutilated or destroyed. She must know that Beowulf is going to use Grendel's dead body as some kind of a trophy, and he does. No mother would want her child to be used in such a way and would fight however she must to prevent it.