CC Madhya 18.8

yathā rādhā priyā viṣṇos
tasyāḥ kuṇḍaṁ priyaṁ tathā
sarva-gopīṣu saivaikā
viṣṇor atyanta-vallabhā
Word for word: 
yathā — as; rādhā — Śrīmatī Rādhārāṇī; priyā — beloved; viṣṇoḥ — of Lord Kṛṣṇa; tasyāḥ — Her; kuṇḍam — lake; priyam — very dear; tathā — similarly; sarva-gopīṣu — among all the gopīs; sā — She; eva — certainly; ekā — alone; viṣṇoḥ — of Lord Kṛṣṇa; atyanta — very; vallabhā — dear.
Translation: 
“ ‘Just as Śrīmatī Rādhārāṇī is most dear to Lord Kṛṣṇa, so Her lake, known as Rādhā-kuṇḍa, is also very dear to Him. Of all the gopīs, Śrīmatī Rādhārāṇī is certainly the most beloved.’
Purport: 

This is a verse from the Padma Purāṇa.