SB 1.4.15

sa kadācit sarasvatyā
 upaspṛśya jalaṁ śuciḥ
vivikta eka āsīna
 udite ravi-maṇḍale
Word for word: 
saḥ — he; kadācit — once; sarasvatyāḥ — on the bank of the Sarasvatī; upaspṛśya — after finishing morning ablutions; jalam — water; śuciḥ — being purified; vivikte — concentration; ekaḥ — alone; āsīnaḥ — being thus seated; udite — on the rise; ravi-maṇḍale — of the sun disc.
Translation: 
Once upon a time he [Vyāsadeva], as the sun rose, took his morning ablution in the waters of the Sarasvatī and sat alone to concentrate.
Purport: 

The river Sarasvatī is flowing in the Badarikāśrama area of the Himālayas. So the place indicated here is Śamyāprāsa in Badarikāśrama, where Śrī Vyāsadeva is residing.