Simplify the following text for a Grade 6 native English-speaking person.
Original: Sarayu river is mentioned in Ramayana . Ramayana mention that city of Ayodhya was situated on the bank of Sarayu river .
Simplified: Later on , according to Ramayana 1.5.6 , the Sarayu flowed beside the ancient city of Ayodhya , which is in the modern day Uttar Pradesh .