One of the five mountains round Rájagaha and one of the beauty-spots of the city (D.ii.116). There was, on one side of it, a black stone called the Kálasilá. This was a favourite haunt of the Buddha and the members of the Order. See e.g., Viii.ii.76, where Dabba Mallaputta is asked by monks to provide for them accommodation there; see also Vin.iii.41.
It was also the scene of the suicide of Godhika and Vakkali (S.i.121; iii.121f) and of the murder of Moggallána by the brigands (J.v.125f; DhA.iii.65).
In the Cúla Dukkhakkhanda Sutta it is said that a large number of Niganthas lived at Kálasilá, never sitting down, undergoing paroxysms of acute pain and agony, following the teachings of Nigantha Nátaputta. The Buddha questioned them as to their practises and preached to them the above-mentioned Sutta, which he afterwards repeated to Mahánáma (M.i.91ff).
Once when the Buddha was dwelling at Kálasilá, he sang the praises of Rájagaha, giving Ananda a chance, if he so desired, of asking him to live on for a kappa; but Ananda did not take his opportunity (D.iii.116).
The books refer to several other visits of the Buddha to Isigilapassa. During one of these visits he heard Vangísa's high eulogy of Moggallána (S.i.194; Thag.1249ff).
In the Isigili Sutta (M.iii.68-71) the Buddha is represented as saying that while the other mountains round Rájagaha - Vebhára, Pandava, Vepulla and Gijjhakúta - had changed their old names, Isigili retained its former name and designation.
Five hundred Pacceka Buddhas once resided in Isigili for a long time; they could be seen entering the mountain, but once entered, there was no more sign of them. Men, observing this, said that the mountain swallowed up the sages and so it came by its name of Isigili (Isí gilatí ti = Isigili).
Buddhaghosa adds (MA.ii.889) that when the Pacceka Buddhas returned from their begging rounds, the rock would open like a folding door to admit them. Within the rock they had made for themselves cloisters, dwelling-houses, etc.