A cave on the side of Gijjhakūṭa, where the Buddha stayed. There he preached the Dīghanakha Sutta to Dīghanakha. Sāriputta was also present, and the sutta led to his attainment of arahantship. MN.i.497 MN.i.501
A conversation which the Buddha had there with Sāriputta is recorded in the Saṃyutta Nikāya. SN.v.233f.