The Mausala Parva, Book 16 of the Mahabharata, describes the events which transpire thirty-six years after the Kurukshetra war: the demise of Krishna, the demise of his brother Balarama and their father Vasudeva, the civil war in which every member of the Yadava clan is killed, and the destruction of the kingdom of Dwaraka. Arjuna arrived in Dwaraka to find out what had happened to Krishna and his clan and he saw the submergence of the kingdom in the sea.
Here’s an excerpt from Arjuna’s description of Dwaraka’s final moments:
“The sea, which had been beating against the shores, suddenly broke the boundary that was imposed on it by nature. The sea rushed into the city. It coursed through the streets of the beautiful city. The sea covered up everything in the city. I saw the beautiful buildings becoming submerged one by one. In a matter of a few moments it was all over. The sea had now become as placid as a lake. There was no trace of the city. Dwaraka was just a name; just a memory.”
The end of Krishna’s clan leads the five Pandava brothers to renounce their own kingdom and begin their march towards heaven.