The site of the Vidura–Uddhava meeting
Vidura came upon the Yamuna and there saw Uddhava: 'kAlena tAvad yamunAm upetya tatroddhavaM bhAgavataM dadarsha' (SB 3.1.24).
River
Yamuna
यमुना
Also known as कालिन्दी · Kalindi
The Yamuna is a sacred river and the site of the meeting between Vidura and Uddhava. At SB 3.1.24, returning from the tirthas of the Sarasvati, Vidura comes upon the Yamuna and there sees Uddhava: 'kAlena tAvad yamunAm upetya tatroddhavaM bhAgavataM dadarsha'.
Śrīmad Bhāgavata Mahāpurāṇa 3.1.24 — Sanskrit Wikisource (pinned chapter page; Devanagari from the cross-validated transcription in validation/sanskrit_skandha3.json)
The bank where Uddhava and Vidura passed the night
SB 3.4.27 calls the Yamuna 'yama-svasuH', the sister of Yama; on her bank Aupagavi, that is Uddhava, passed that night with Vidura hearing the tale of the qualities of the Lord of universal form, as though it were a moment. At SB 3.4.36 the same river is called Kalindi.