Of all the gopīs, Rādhārāṇī is the dearmost. Similarly, the lake known as Rādhā-kuṇḍa is very dear to the Lord because it is very dear to Śrīmatī Rādhārāṇī.
(Sri Caitanya Caritamrta----2:18:7---translation).

The attraction of Rādhā-kuṇḍa is as sweet as that of Śrīmatī Rādhārāṇī. Similarly, the glories of the kuṇḍa (lake) are as great as Śrīmatī Rādhārāṇī’s.
(Sri Caitanya Caritamrta----2:18:11---translation).

Because of its wonderful transcendental qualities, Rādhā-kuṇḍa is as dear to Kṛṣṇa as Śrīmatī Rādhārāṇī. It was in that lake that the all-opulent Lord Śrī Kṛṣṇa performed His pastimes with Śrīmatī Rādhārāṇī with great pleasure and transcendental bliss. Whoever bathes just once in Rādhā-kuṇḍaattains Śrīmatī Rādhārāṇī"s loving attraction for Śrī Kṛṣṇa. Who within this world can describe the glories and sweetness of Śrī Rādhā-kuṇḍa?
(Sri Caitanya Caritamrta----2:18:12---translation).

Śrī Caitanya Mahāprabhu thus offered prayers to Rādhā-kuṇḍa. Overwhelmed by ecstatic love, He danced on the bank, remembering the pastimes Lord Kṛṣṇa performed on the bank of Rādhā-kuṇḍa.
(Sri Caitanya Caritamrta----2:18:13---translation).

Śrī Caitanya Mahāprabhu then marked His body with tilaka made from the mud of Rādhā-kuṇḍa, and with the help of Balabhadra Bhaṭṭācārya, He collected some of the mud and took it with Him.
(Sri Caitanya Caritamrta----2:18:14---translation).

The holy place known as Mathurā is spiritually superior to Vaikuṇṭha, the transcendental world, because the Lord appeared there. Superior to Mathurā—Purī is the transcendental forest of Vṛndāvana because of Kṛṣṇa's rāsa-līlā pastimes. And superior to the forest of Vṛndāvana is Govardhana Hill, for it was raised by the divine hand of Śrī Kṛṣṇa and was the site of His various loving pastimes. And, above all, the superexcellent Śrī Rādhā-kuṇḍa stands supreme, for it is overflooded with the ambrosial nectarean prema of the Lord of Gokula, Śrī Kṛṣṇa. Where, then, is that intelligent person who is unwilling to serve this divine Rādhā-kuṇḍa, which is situated at the foot of Govardhana Hill?
(Nectar of Instruction).

It is also at Govardhana Hill that Kṛṣṇa tends the cows with His cowherd friends, and there also He had His rendezvous with His most beloved Śrī Rādhā and engaged in loving pastimes with Her. Rādhā-kuṇḍa, at the foot of Govardhana, is superior to all because it is there that love of Kṛṣṇa overflows. Advanced devotees prefer to reside at Rādhā-kuṇḍa because this place is the site of many memories of the eternal loving affairs between Kṛṣṇa and Rādhārāṇī (rati-vilāsa).
In Caitanya-caritāmṛta (Madhya-līlā) it is stated that when Śrī Caitanya Mahāprabhu first visited the area of Vrajabhūmi, He could not at first find the location of Rādhā-kuṇḍa. This means that Śrī Caitanya Mahāprabhu was actually searching for the exact location of Rādhā-kuṇḍa. Finally He found the holy spot, and there was a small pond there. He took His bath in that small pond and told His devotees that the actual Rādhā-kuṇḍa was situated there. Later the pond was excavated by Lord Caitanya's devotees, headed first by the six Gosvāmīs, such as Rūpa and Raghunātha dāsa. Presently there is a large lake known as Rādhā-kuṇḍa there. Śrīla Rūpa Gosvāmī has given much stress to Rādhā-kuṇḍa because of Śrī Caitanya Mahāprabhu's desire to find it. Who, then, would give up Rādhā-kuṇḍa and try to reside elsewhere? No person with transcendental intelligence would do so.
(Nectar of Instruction).

Why is Rādhā-kuṇḍa so exalted? The lake is so exalted because it belongs to Śrīmatī Rādhārāṇī, who is the most beloved object of Śrī Kṛṣṇa. Among all the gopīs, She is the most beloved. Similarly, Her lake, Śrī Rādhā-kuṇḍa, is also described by great sages as the lake that is as dear to Kṛṣṇa as Rādhā Herself. Indeed, Kṛṣṇa's love for Rādhā-kuṇḍa and Śrīmatī Rādhārāṇī is the same in all respects. Rādhā-kuṇḍa is very rarely attained, even by great personalities fully engaged in devotional service, not to speak of ordinary devotees who are only engaged in the practice of vaidhī bhakti.
It is stated that a devotee will at once develop pure love of Kṛṣṇa in the wake of the gopīs if he once takes a bath in Rādhā-kuṇḍa. Śrīla Rūpa Gosvāmī recommends that even if one cannot live permanently on the banks of Rādhā-kuṇḍa, he should at least take a bath in the lake as many times as possible. This is a most important item in the execution of devotional service.
(Nectar of Instruction).