The place name is Drumatulya. It is mentioned in Valmiki Ramayana, Yuddha Kanda, Sarga 22.
रामस्य वचनम् श्रुत्वा तम् च दृष्ट्वा महाशरम् || २-२२-३०
महोदधिर्महातेजा राघवम् वाक्यमब्रवीत् |
Hearing Rama's words and seeing that powerful arrow, the large splendid Ocean spoke the following words to Rama:
उत्तरेणावकाशोऽस्ति कश्चित्पुण्यतरो मम || २-२२-३१
द्रुमकुल्य इति ख्यातो लोके ख्यातो यथा भवान् |
Towards my northern side, there is a holy place. It is well known as Drumatulya, in the same way as you are well known to this world.
उग्रदर्शनकर्माणो बहवस्तत्र दस्यवः || २-२२-३२
आभीरप्रमुखाः पापाः पिबन्ति सलिलम् मम |
Numerous robbers of fearful aspect and deeds, having the sinful Abhiras as their chief, drink my waters there.
तैर्न तत्स्पर्शनम् पापम् सहेयम् पापकर्मभिः || २-२२-३३
अमोघः क्रियताम् राम तत्र तेषु शरोत्तमः |
I am not able to bear that touch of those wicked people, the evil doers, O, Rama! Let this excellent arrow with out vain be released over them there.
तस्य तद्वचनम् श्रुत्वा सागरस्य महात्मनः || २-२२-३४
मुमोच तम् शरम् दीप्तम् परम् सागरदर्शनात् |
Hearing those words of the high-soled Ocean, Rama released that excellent and splendid arrow towards that place as directed by the ocean.
तेन तन्मरुकान्तारम् प्^इथिव्याम् किल विश्रुतम् || २-२२-३५
विपातितः शरो यत्र वज्राशनिसमप्रभः |
The place where the arrow, whose splendor was akin to that of a thunder and a thunder bolt, was descended by Rama- that place is indeed famous as desert of Maru* on this earth.
- Maru�Malwar in Rajastan (India)