Where did sage Kapil reside?

Question

There is a story of King Sagar's sixty thousand sons digging up the earth while looking for the Ashwamedh horse that Indra had stolen. A lot of people would know the story so I am not posting it in entirety here. My concern is with the location where they find the horse - the hermitage of Sage Kapil & its location. As per the Mahabharat:

Thus they went on digging the ocean, which was the abode of Varuna and an exceedingly long space of time expired in this work, but still the horse was not found. Then, O lord of earth! towards the north-eastern region of the sea, the incensed sons of Sagara dug down as far as the lower world, and there they beheld the horse, roaming about on the surface of the ground. And they saw the magnanimous Kapila, who looked like a perfect mass of splendour.

I want to know if there are more details in any other scripture about this underground realm where they meet Sage Kapil who is an avatar of Lord Vishnu?

Answer 1

Sage Kapila was residing in Rasatala. This is one of the seven worlds below the Bhu loka. The fourteen worlds are

1. Satya-loka
2. Tapa-loka
3. Jana-loka
4. Mahar-loka
5. Svar-loka
6. Bhuvar-loka
7. Bhu-loka
8. Atala-loka
9. Vitala-loka
10. Sutala-loka
11. Talatala-loka
12. Mahatala-loka
13. Rasatala-loka
14. Patala-loka

From Valmiki Ramayana, Bala Kanda Sarga 40,

pitur vacanam āsādya sagarasya mahātmanaḥ |
ṣaṣṭiḥ putra sahasrāṇi rasātalam abhidravan || 1-40-12

On catching up the words of their father, the great-souled Sagara, his sixty thousand sons rushed towards the surface of the rasaa tala, the netherworld.

Sixty thousand sons of Kapila reach rasatala and dig the earth in different directions circumabulaitng the elephants which bear the quarters of the earth known as Ashtadiggajas. Finally, they see Kapila and also the sacrificial horse. They mistake him as the thief of the sacrificial horse and attack on him. Sage Kapila burns down them to ashes.

There is a brief description of this world in Srimad Bhagavatam Skandha 5 chapter 24

Beneath Mahātala is the planetary system known as Rasātala, which is the abode of the demoniac sons of Diti and Danu. They are called Paṇis, Nivāta-kavacas, Kāleyas and Hiraṇya-puravāsīs [those living in Hiraṇya-pura]. They are all enemies of the demigods, and they reside in holes like snakes. From birth they are extremely powerful and cruel, and although they are proud of their strength, they are always defeated by the Sudarśana cakra of the Supreme Personality of Godhead, who rules all the planetary systems. When a female messenger from Indra named Saramā chants a particular curse, the serpentine demons of Mahātala become very afraid of Indra.

It is said by Narada while searching a best groom for the daughter of Matali that it is one of the happiest places.

From Mahabharata Udyoga Parva

The couplet that was sung by the dwellers of Rasatala in day of old, is still heard to be recited in the world by the persons of learning. That couplet is this,--Neither in the region of the Nagas, nor in Swarga, nor in Vimana, nor in Tripishtapa is residence so happy as in Rasatala!'"

It is probable that other puranas also talk about Rasatala.

Answer 2

I don't know if there other itihaasaas which clarify. However, from the living gurus words, Kachi Kamakoti periyavaal, KapilaAsharama became California.

Shree gurubyo namah.