Vaishnava Samhita. Meera Charitam II. Vol III Book VI Chp 14 Shloka 7 May 2, 2017 Subhashri Vyas अन्तर्धानं गते कृष्णे समुद्रः सप्तमेsहनि |नाशयामास नगरीं त्यक्त्वा भगवदालयम् ||On the seventh day after Bhagavan ascended his Divine Abode the sea engulfed Dwaraka. But the temple of Lord Krishna alone remains intact.
