Avraham spends considerable money and effort to acquire the cave of machpelah. I think the medrash mentions that Adam and Chava were buried there. My question is, is the cave of machpelah special because of the people who were buried there, or was that area special and therefore the Avot and Emaot wanted to be buried there? If the cave of machpelah has some sort of significance apart from the people who are buried there, what is it?
The source of the name Maaras Hamachpeila could shed some light on this question. - According to one opinion in Eiruvin 53a, either Rav or Shmuel (the Gemara doesn't say which one said it) says the cave is named because it is "doubled with couples" i.e. there are many couples there. This would seem to imply that its main significance is who is buried there. (The other opinion says that it was named for its multiple levels.)
On the other hand, the Yalkut Reuveini brings from the Zohar on Chayei Sarah that this cave is the entranceway through which souls enter Gan Eden. This is why, the Zohar says, Adam chose to bury Chava there, and may very well be why Avraham wanted to bury Sarah there.
After Rav Avrohom Azulai (1570-1643) in his sefer Chesed L'Avrohom explains that the lower Garden of Eden is entered by way of the Garden, and that both the Garden and Gehinom - the dwelling place of harmful creatures and angels of destruction - are located on the north side of this lowly world, he writes:
Because it is difficult for both the living and the dead to go to the Garden of Eden because of the fear of the harmful creatures of Gehinom who are located on the north side of the world, Hashem’s wisdom decreed the making of an underground tunnel from the Cave of Machpelah which is in Chevron to a place outside of this lowly world next to the Garden, in order that the souls of the tzaddikim can go there directly without encountering any harmful creatures.
Adam and Chavah (Eve) knew this secret and therefore they endeavored to be buried there, and after they were buried there the mouth of the cave was sealed so that no one would know about the specialness of the place.
But on the day that Avrohom went with his son Yishmael to take three bulls from his herd, the angel Refael, on a mission from Hashem, secretly followed him, and after Avrohom took two bulls and gave them to the lad to take home, Refael appeared before him in the guise of a very superior looking bull (this is alluded to by the name פר אל - רפאל - an superior bull), and thus this was the third bull that Avrhom planned to take. But when Avrohom tried to take it, the bull evaded him and ran a little way off.
This process repeated itself until it brought him to the entrance of the Cave of Machpelah and the entrance of the cave opened. When he saw Adam and Chavah buried there and smelled the fragrance of the Garden of Eden, he immediately understood the specialness of the place and desired that his burial should be there.
The bull now delivered himself into the hands of Avrohom, but when he reached his tent he only found two bulls, and so Avrohom had to create a third bull using the Sefer Yetzirah in order not to cause distress to his guests, because if he returned to the herd to take a third bull the time when it is fitting to eat would have passed. This is what the posuk in Bereishis 18:8 means “and he took…the young bull which he had made” - which he had actually made.
Full text in English can be found here.