Valmiki Ramayana Kishkindha Kanda Sarga 9 Shloka 11

सः असुरः that demon, धरण्याः on earth, दुर्गम् difficult passage, तृणैः by heaps of grass, आवृतम् covered, महत् great, विवरम् a hole, प्रविवेश entered, आवाम् both of us, आसाद्य reaching, विष्ठितौ we took position

'The demon entered into a hole (cave) covered with a heap of grass, difficult, therefore, of access. Both of us reached there and took position.