Shri Vyasadasa Charitam I. Vol II Book VI C 1 Shlokas 6 - 7
सेवाकुञ्जसमीपे स वसन्नित्यं दृढव्रतः
राधिकाकृष्णयोः सेवां चकार प्रेमपूर्वकम् ||
इदमेव परं सौख्यं भावुकानां महात्मनाम्
राधामाधवयोर्दास्यं निकुञ्जे लभ्यते यदि ||
The steadfast Vyasadeva resided near the Seva Nikunja of the divine couple and was ever engaged in the sacred service of Shri Krishna and Radha. The great ones filled with loving devotion find amazing happiness when they get the chance of serving Shri Radha and Krishna in the Nikunja.