CC Madhya 18.222
daśa-dina triveṇīte makara-snāna kailā
Śrī Caitanya Mahāprabhu finally arrived at Prayāga and for ten successive days bathed in the confluence of the rivers Yamunā and Ganges during the festival of Makara-saṅkrānti [Māgha-melā].
Actually the word triveṇī indicates the confluence of three rivers — namely the Ganges, Yamunā and Sarasvatī. Presently the Sarasvatī River is not visible, but the river Ganges and the river Yamunā merge at Allahabad.