A city in the Bhagga country, of which it was probably the capital (See, e.g., Sp.iv.862). The Buddha spent the eighth vassa there (BuA.3). Near the city was the Bhesakalāvana where the Buddha stayed.
During his visits there he preached the Anumāna Sutta (M.i.95f ) and the Bodhirāja Sutta (M.ii.91f). The city was the residence of Nakulapītā and his wife, with whom the Buddha had several interviews. (E.g., A.ii.61; iii.295 f; iv.268; S.iii.1; iv.116).
It is said that once, when the Buddha was at Sumsumāragiri, he saw with his divine eye Moggallāna at Kallavālamutta half asleep, and appeared before him and admonished him (A.iv.85).
On another occasion, he saw Anuruddha in the Veluvana in the Ceti country, pondering over the seven Mahāpurisavitakkas, and appeared before him to encourage him (A.iv.228f). Both incidents show that the Buddha visited Sumsumāragiri quite early in his career, in the first year after the Enlightenment. Moggallāna also stayed in Sumsumāragiri, and there Māra is said to have entered his stomach and to have given him trouble (M.i.332f.; cf. Thag.vs.1208).
Sumsumāragiri was the birthplace of Sirimanda Thera (ThagA.i.462) and the scene of the meditations of Singālakapitā.
Several Vinaya rules were passed during the Buddha's stay at Sumsumāragiri (Vin.ii.127; iv.115f; 198f).
The Dhonasākha Jātaka was preached there (J.iii.157f). Prince Bodhi, the governor of the Bhagga country, evidently lived in Sumsumāragiri, and it was there that he had his famous palace, called Kokanada.
It is said (MA.i.292; SA.ii.181) that the city was so called because when it was being built a crocodile (sumsumāra) made a noise in a lake near by.