Describe the differences between Grendel's dwelling and Herot, Hrothgar's hall?

Heorot is Hrothgar's great mead hall, constructed for his warriors. It is a place for gathering... and Hrothgar's palace. It is described as "the foremost of halls under heaven', constructed of timber and gilded in gold.

Then, as I have heard, the work of constructing a building
Was proclaimed to many a tribe throughout this middle earth.
In time—quickly, as such things happen among men—
It was all ready, the biggest of halls.
He whose word was law
Far and wide gave it the name "Heorot".

The men did not dally; they strode inland in a group
Until they were able to discern the timbered hall,
Splendid and ornamented with gold.
The building in which that powerful man held court
Was the foremost of halls under heaven;
Its radiance shone over many lands.

Grendel's lair is described as bring "down in the darkness".

. . A powerful monster, living down
In the darkness