In Raghuvamsa 6th Canto and Verse 58 or 59 

अथोरगाख्यस्य पुरस्य नाथं first foot says about Nagapura or Uragapura 

Mallinatha explains as कान्यकुब्जतीरवर्तिनागपुरस्य but this seems to be a mistake as Kanouj is on the North of India , whereas the poet in further verses clearly places it on the south. 

And on further search I found Arunagirinatha and Narayana in the commentary to the above mentioned verse give the details as the place  in the bank of the river कायकुटी

पाण्ड्येषु कायकुटी नाम नदी प्रवहति तस्मिन् तीरे नागपुराख्यं...

Does any one knows about this river or its modern name kindly inform.

I also believe that even Mallinatha has written कायकुटी as the name is not famous that must be due to लिपिसारूप्य scribal error occurred

Thanks