As a physical river, in the oldest texts of the Rig Veda she is described as a "great and holy river in north-western India," but in the middle and late Rig Vedic books she is described as a small river ending in "a terminal lake (samudra)." As the goddess Sarasvati, the other referent for the term "Sarasvati" which developed into an independent identity in post-Vedic times, she is also described as a powerful river and mighty flood. The Sarasvati is also considered by Hindus to exist in a metaphysical form, in which it formed a confluence with the sacred rivers Ganges and Yamuna, at the Triveni Sangam. According to Michael Witzel, superimposed on the Vedic Sarasvati river is the heavenly river Milky Way, which is seen as "a road to immortality and heavenly after-life."