Gemara

(Mishnah - R. Akiva): One (who sold his house) did not sell the pit or cistern, even if he wrote 'the depth and height.' However, the seller did not retain a path to them, and he must buy this from the buyer;

Chachamim say, he retained a path to them.

R. Akiva agrees that if he said '(I sell the house) except for the pit and cistern', he retained a path to them.

Bava Basra 63b (Rav Dimi of Neharda'a): If one sells his house, it is not enough to write 'the depth and height.' He must write also 'from the Tehom (the depth below the earth) to the sky'.

This is because Stam (without specifying), the seller keeps the depth and height (rights to dig below, and a roof with a wall around it). Therefore, 'the depth and height' includes only these. He needs 'from the Tehom to the sky' to include the pit, cistern and tunnels.

64a (Ravina) Question: Why must the Mishnah teach both a pit and cistern?

Answer (Rava Tofa'ah - Beraisa): A pit and cistern are essentially the same; a pit is merely a hole, a cistern is a building (of stones) inside a pit.

65a (Rav Huna citing Rav): The Halachah follows Chachamim.

(R. Yirmeyah bar Aba citing Shmuel): The Halachah follows R. Akiva.

R. Yirmeyah bar Aba: Many times I said in front of Rav that the Halachah follows R. Akiva, and he did not respond!

Rav Huna: How do you learn the argument?

R. Yirmeyah: R. Akiva says that a person sells stingily, Chachamim say that a person sells generously.

Rav Huna: He did not respond because the Halachah is, a person sells stingily. According to your version of the argument, the Halachah follows R. Akiva.

Suggestion (Ravina): Rav and Shmuel hold as they taught elsewhere. (It seems that Ravina and Rav Nachman hold that Rav and Shmuel argue, i.e. also Shmuel had our text of the Mishnah.)

(Rav Nachman citing Shmuel): Brothers who divide an inheritance (are like buyers and sellers); they do not have rights to walk over each other's property (because they sell generously)...

(Rav): They have all these rights against each other.

Question (Rav Nachman, to Rav Huna): Is the Halachah like us (Shmuel and his Talmidim), or like you (and Rav)?

Answer (Rav Huna): It is like you, for you are close to the Reish Galusa and see how the judges rule. (Rav Huna holds that Rav and Shmuel argue only about brothers. Alternatively, Rav Huna answered 'if Shmuel rules that people sell generously, like you say, the Halachah follows him in both cases.)

Rishonim

Rif and Rosh (Bava Basra 35a and 4:8): Rav Huna said that Rav rules like Chachamim, that people sell stingily. Shmuel rules like R. Akiva, that people sell generously. Rav Huna admitted that the Halachah follows Shmuel.

Nimukei Yosef (DH Masnisin): The buyer does not acquire the pit or cistern because its usage, to draw water, is unlike the use of a house. R. Akiva says that if he said 'except for the pit and cistern', he need not buy a path. Since he did not say that he sells 'the depth and height', it was clear that he kept the pit or cistern, so 'except for the pit and cistern' teaches that he keeps a path to them.

Nimukei Yosef (33a DH ha'Mocher and 33b DH v'Ika): If he wrote 'I did not leave over anything in this sale', the pit or cistern is sold. R. Yonah was unsure about this. Some say that 'I did not leave over anything' helps only for things such a house and a building, for these names are interchangeable, but not to include pit or cistern with a sale of a house.

Nimukei Yosef (35b DH Masnisin): The Rashba says that if he delineated the borders and said 'I sell everything inside', also the pit or cistern is sold.

Rosh (2): Even if he delineated the borders and said 'I did not leave over anything in this sale', the pit or cistern is not sold. Since they are not included in the sale of a house, 'this sale' does not apply to them. One must write 'from the Tehom to the sky' to include the pit, cistern and tunnels (63b). We normally write 'I did not leave over in this sale', and the Gemara did not say that this suffices!

Beis Yosef (DH u'Mah she'Chosav v'Lo): The Rif and Rambam hold that delineating the borders does not help only regarding an inner room, but it could help for a Yatzi'a (lean-to). A pit or cistern is like a Yatzi'a.

Darchei Moshe (1): The Rif and Rambam could hold that a pit or cistern is like an inner room. All agree that delineating the borders does not include an inner room.

Rambam (Hilchos Mechirah 25:2): One who sold his house did not sell the pit dug into the ground or the cistern built in the pit, even if he sold 'the depth and height.'

Rambam (3): The seller must buy a path to them in order to enter to use them, for people sell generously. If he 'except for the pit and cistern', he need not buy a path. He enters the buyer's house until his pit, and fills (his Keli).

Poskim

Shulchan Aruch (CM 214:2): One who sold his house did not sell the pit or cistern (Rema - even if he delineated the outer borders), even if he sold 'the depth and height.'

Source (Gra 7): On 61b, we said that if everyone calls a Birah (building) a Birah, even if he delineated boundaries of the entire Birah, surely it is not included in the sale of a house. The same applies to a pit or cistern.

Rema: He also wrote 'I did not retain anything in this sale.' Some disagree in any case when he wrote this.

SMA (9,10): This comment of the Rema is part of the previous one (he delineated the outer borders and wrote 'I did not retain anything in this sale'). If he delineated the outer borders and said 'acquire everything inside', this is better, and all agree that he acquires everything inside.

Gra (8): The opposing opinion holds that 'I did not retain' does not help only against the connotation of his words (most people don't call a Birah a house).

Shulchan Aruch (ibid.): The seller must buy a path to them in order to enter to use his pit or cistern. If he sold 'except for the pit or cistern', he need not buy a path.

SMA (11): If the seller needed to stipulate to retain something, e.g. he sold a tree and retained its fruits, all agree that he kept a path.