Mahabharata 5.100.1

नारद उवाच · nārada uvāca

इदं रसातलं नाम सप्तमं पृथिवीतलम्यत्रास्ते सुरभिर्माता गवाममृतसंभवा

idaṃ rasātalaṃ nāma saptamaṃ pṛthivītalamyatrāste surabhirmātā gavāmamṛtasaṃbhavā

Our plain-language meaning of this verse is waiting for scholar review.