Valmiki Ramayana Aranya Kanda Sarga 11 Shloka 68

तटाकवनशोभितः adorned with lakes and forests, अयम् this, येन by whom, विप्रानुकम्पया congenial to brahmins, इदम् this, दुष्करम् difficult, कर्म action, कृतम् is done, तस्य his, भ्रातुः brothers, आश्रम: hermitage.

This hermitage surrounded by beautiful lakes and forests belongs to his brother (Sudarsana). Out of sympathy for Agastya, he has accomplished this difficult task.