On the bank of which river, Gautam Buddha attained enlightenment?

Q. On the bank of which river, Gautam Buddha attained enlightenment?
Answer: Niranjana
Notes: Gautam Buddha attained enlightenment on the bank of river Niranjana. He attained the enlightenment on the night of Vaishakh Purnima while sitting below the Sacred Fig Tree i.e. Peepal tree in the state of Samadhi. The tree is now known as the Bodhi Tree.