Was Bali trampled by Vamana?

 Vamana did not trample Bali.  It is famous that Mahabali donated three feet to Vamanamurthy with two feet, and when he measured the whole universe with two feet in Vishwarupa, he showed his head to place the third foot.  But Vamana did not trample Mahabali.  Satisfied by Mahabali's devotion, he was blessed with the special world of Suthalam and the status of Indra in the next Manvantara.

  Mahabali comes from the underworld?
 Lord Mahabali was not sent to hell.  But to a world called Suthalam, which is better than heaven.  Bhagavatam also says that those who live there will not be affected by diseases or vermin.